BACTERIUM COLI COMMUNE. 305 



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 is still a subject for 

 study, and some have even gone so far as to regard 

 them as modifications of the same species, though in 

 the present state of our knowledge this is certainly 

 overstepping the mark. 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 of but 

 trifling moment, and its presence in these localities was 

 usually explained as accidental. Its repeated appearance, 

 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 a great deal has been written concerning the 

 possible pathogenic nature of this organism. 



The fact that it is always with us in most intimate 

 association with certain of our life processes, together 

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



