1 56 BACTERIA 



bubbles. On agar plates surface colonies are like typhoid, only 

 they are thicker and moister. If litmus is added to this medium, a 

 red zone forms about the colonies, due to the presence of lactic acid. 

 In agar tubes the growth is more luxuriant and resembles typhoid. 

 In litmus bouillon it rapidly reddens the litmus, clouds the medium, 

 and deposits a slimy sediment. In milk it always produces coagu- 

 lation. On potato it grows more rapidly and luxuriantly than 

 typhoid, at first yellowish-white, which later changes to yellowish- 

 brown. It is slimy. 



Chemical Activities. Produces color on potato only. Sugars 

 are fermented with the production of H, CO 2 and some N. Some 

 varieties ferment cane sugar. Produces lactic, acetic and formic 

 acids, also indol abundantly, and H 2 S. It decomposes urea. There 

 are a great many varities of colon bacilli having very different 

 chemical activities. 



Habitat. Found always in the intestinal contents of most ani- 

 mals and man. Also in streams and rivers that run through farm 

 lands and by towns. While it is difficult to find typhoid bacilli in 

 drinking water, the colon bacilli are easily found. If in abundance, 

 it indicates great fecal pollution. In milk it is often found, where 

 it plays an important part in souring. 



Pathogenesis. It is pathogenic to rabbits and guinea pigs, 

 causing peritonitis if injected into the peritoneal cavity. In man 

 it plays rather a subordinate pathogenic role, but it has been found 

 the causal agent of some cases of suppurative appendicitis, peri- 

 tonitis, and cystitis. It may attack the lungs and meninges of 

 feeble children, and cause death by setting up a pneumonia or 

 meningitis. During the agonal period in wasting diseases it may 

 cause terminal infection and death. Colon bacilli encysted in the 

 liver and kidney have been found by Adami in cirrhosis of these 

 organs, and it is believed by him to be partly the cause of these 

 diseases; chronic infections of the rectum are due to this organism. 



Agglutination. Animals immunized against colon bacilli by 

 repeated injections, exhibit agglutinins in their blood. 



