INFECTIONS OF THE DIGESTIVE TRACfr 101 



nomenon. After a time the substituting microorganism 

 loses its prominent place and in its stead the obligate 

 bacteria of the tract again become dominant. 



The phenomenon of substitution is one that most 

 frequently involves temporary replacements of the colon 

 bacilli in the lower part of the large intestine and also in 

 higher portions. An example of what is meant by such 

 substitution is afforded by the folio whig case. A woman 

 of twenty-five years of age developed measles and soon 

 after convalescence became ill with what was apparently 

 a condition of mucous colitis, lasting about one month 

 and attended by slight fever. Studies of the flora made 

 toward the end of the period of mucous colitis showed 

 that the faecal fields contained an excessive number of 

 diplococci, and the sediments of the fermentation tubes 

 exhibited streptococcal growths in great abundance. 

 On litmus gelatin plates made from faecal suspensions 

 it was found that the dominant organism resembled 

 colon bacilli in appearance, but differed from them in 

 forming acid very slowly. Many colonies were fished 

 from these plates and studied, but none were found which 

 could be called colon bacilli. The organisms obtained 

 differed from colon bacilli in making no indol and in 

 possessing only feeble powers of gas production and of 

 acid formation on glucose. They irregularly fermented 

 levulose and lactose. They coagulated milk only after 

 a lapse of ten days, and then the coagulation was in- 

 complete. They were actively motile Gram-negative 

 bacteria. Two weeks later, during the progress of con- 

 valescence from the condition of mucous colitis, it was 



