504 APPLICATION OF METHODS OF BACTERIOLOGY 



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 as but varieties of one and 

 the same species, though in the present state of our knowl- 

 edge this is 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 considered 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 occasionally 

 observed that, under favorable circumstances, bacillus coli 

 disseminated from its normal habitat and appeared in 

 remote organs, often associated with diseased conditions. 

 This was at first considered of but little importance, and its 

 presence in these localities was viewed as accidental. Its 

 repeated appearance, however, in different organs of the 

 body and the frequency of its association with pathological 

 conditions, ultimately attracted attention to it, and in 

 consequence a great deal has been written concerning the 

 possible pathogenic nature of this organism. 



The fact that it is a commensal species, always intimately 

 associated with certain of our life-processes, together with 

 the fact that it is known to appear in organs other than 

 that in which it is normally located, and that its occurrence 

 in diseased conditions is not rare, justifies the opinion that 

 it is one of the most important of the micro-organisms with 

 which we have to deal. 



