322 BACTERIOLOGY. 



BACTERIUM COLI COMMUNE (colon bacillus ; bacillus 

 Neapolitanus of Emmerich). This organism was dis- 

 covered by Escherich,in 1885, in the intestinal discharges 

 of milk-fed infants. It has since been demonstrated to 

 be a normal inhabitant of the intestines of man and of 

 certain domestic animals (cattle, hogs, dogs). 



For a time after its discovery it was considered of but 

 little importance and attracted attention only because 

 of its resemblance, in certain respects, to the bacillus of 

 typhoid fever, with which it was occasionally confounded. 

 In this particular it still serves as a subject for study. Some 

 have even gone so far as to regard them but as varieties of 

 one and the same species, though in thepresent state of our 

 knowledge this is certainly an assumption for which, as 

 yet, there are not sufficient grounds. That they possess 

 in common certain general points of resemblance and 

 often approach one another in some of their biological 

 peculiarities is true ; but, as we shall learn, they each 

 possess peculiarities, which, when taken together, render 

 their differentiation from one another a matter of but 

 little difficulty. 



With the wider application of bacteriological methods 

 to the study of pathological processes it was occasion- 

 ally observed that, under favorable circumstances, this 

 organism was disseminated from its normal habitat and 

 appeared in remote organs, often associated with diseased 

 conditions. This was also, at first, considered as of but 

 trifling moment, and its presence in these localities was 

 usually explained as accidental. Its repeated appear- 

 ance, however, in different parts of the body outside of 

 the intestines, and the frequency of its association with 

 pathological conditions, ultimately attracted attention to 

 it, and in consequence during the past two or three years 



