CHAPTER VI. 
THE BACILLI OF THE COLON, TYPHOID, 
DYSENTERY GROUP. 
These organisms are usually grouped together 
because of the similarity in their appearance and man¬ 
ner of growth upon artificial culture media. All the 
members of this group are short, rod-shaped, often 
forming chains, but never forming spores. They are 
all motile and Gram negative. They are distinguished 
from one another by the way they ferment sugars and 
produce acid in culture media. 
Under the name of colon bacilli are grouped a 
number of varieties very closely related, which are usu¬ 
ally harmless parasites living in the bodies of man and 
animals, but which at times become pathogenic and 
cause infection. The colon bacillus itself, properly 
called the Bacillus coli communis , is a constant inhabi¬ 
tant of the intestine in man and animals. In nature it 
is commonly found in soil, air, water, and milk. Just 
what function it performs in the intestine is not known 
positively, but it probably assists in breaking down 
food materials into simpler form so that they can be 
absorbed. Some believe that the colon bacillus elab¬ 
orates a substance harmful to disease-producing bac¬ 
teria in the intestines. 
Once the colon bacillus has invaded the walls of 
the intestine, it is capable of setting up an infection. 
It has been found to be the cause of kbscess of the liver, 
inflammations of the gall-bladder, the urinary bladder, 
the pelvis of the kidney, and the pancreas. It is 
frequently the cause of peritonitis in cases of rup- 
(59) 
The 
colon 
bacillus 
