INTESTINAL OR COLON-TYPHOID GROUP 265 



exaggerated. Failure to distinguish between the true colon group 

 and the group of meat-poisoning bacilli is doubtless responsible 

 for some of the statements attributing pronounced pathogenic 

 properties to B. coli. The frequent ascription of various inflam- 

 matory processes, particularly those occurring in the appendix 

 and peritoneum, to the unaided activities of B. coli, appears to be 

 without sufficient justification. Many of the cases reported rest 

 on the evidence derived from simple aerobic cultivation, and the 

 possible concurrence of anaerobic or other organisms not growing 

 by ordinary methods has not been excluded." The preceding 

 was written with pathogenesis for the human body in mind, but 

 the conclusions are even more true with reference to its patho- 

 genesis for animals. Many diseases in domestic animals have 

 been ascribed to infection with varieties of B. coli from insufficient 

 evidence. It has been shown that even in the normal body colon 

 bacilli sometimes escape from the intestines, and are to be found 

 in the mesenteric lymph-nodes, and occasionally in some of the 

 other internal organs. 



Experimental Evidence of Pathogenesis. The intraperitoneal 

 injection of broth cultures of B. coli into the guinea-pig results 

 in the death of the animal, usually within three days. Animal 

 experimentation has demonstrated quite conclusively that there 

 are considerable differences in virulence of the colon bacillus iso- 

 lated from different animals or from the same animal at different 

 times. 



Character of Lesions and Disease Produced. B. coli has been 

 isolated from suppurations in pure culture. In man it is known 

 occasionally to invade the gall-bladder, and is a common cause of 

 cholecystitis. It may serve as a nucleus for gall-stones, and is 

 probably instrumental in their formation by the precipitation of 

 cholesterin. Inflammation of the ureters and of the urinary 

 bladder is commonly caused in man by organisms that cannot be 

 differentiated from typical B. coli. It has been reported as the 

 cause of calf diarrhea or white scours, and from malignant catarrh 

 in cattle. It is possible that these organisms are mere closely 

 related to the B. enteritidis. Usually the colon bacillus does not 

 give rise to putrefactive products, and must be regarded as a 

 harmless or even useful commensal. 



