INFECTIONS OF THE DIGESTIVE TRACT 151 



digestive tract and as infective agents inside the tract. 

 We are not concerned here with those examples of colon- 

 bacillus infection in which the organisms find their way 

 into the urinary tract from the exterior and set up a 

 cystitis or pyelitis. Nor shall I do more than refer to 

 those infections in which colon bacilli have passed during 

 life through some local spot of injury in the digestive 

 tract into the blood or the peritoneal cavity, setting up 

 in the former case a septicaemia or pyaemia, and in the 

 latter a peritonitis. With less serious consequences 

 than these, the colon organisms probably often pass 

 temporarily from the digestive tract by way of the blood, 

 to the kidney, with a resulting pyelonephritis or pyelitis, 

 or at least a bacteriuria. It is noteworthy that the 

 localization of colon bacilli under such pathological 

 conditions as these is often attended by a heightened 

 virulence for small animals as compared with the vir- 

 ulence of the original bacteria of the intestine. 



The question which does especially interest us here is 

 whether the colon bacilli of an individual ever do injury 

 to that individual while still confined to the digestive 

 tract. In attempting to answer it, I must divide the 

 question into two one relating to acute effects of the 

 colon bacilli, the other relating to prolonged pathological 

 activities. 



If we go back to the time when Escherich first de- 

 scribed B. coli commune as an obligate inhabitant of the 

 human digestive tract, we find that there was a dis- 

 position to regard it as the cause of various diarrhreal 

 affections. A close examination of facts relating to the 



