454 BACTERIOLOGY. 



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, 

 bacillus coll disseminated from its normal habitat 

 and appeared in remote organs, often associated witu 

 diseased conditions. This was at first considered 

 of but little importance, and its presence in these 

 localities was usually regarded 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 few years a great deal has been written concerning 

 the possible pathogenic nature of this organism. 



The fact that it is a commensal species, always inti- 

 mately 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. 



While not generally considered a pathogenic organ- 

 ism, there is, nevertheless, sufficient evidence to war- 

 rant the statement that under favorable conditions of 

 reduced vitality on the part of the animal tissues, this 

 organism may assume pathogenic properties, so that its 

 presence in diseased conditions is not always to be con- 

 sidered as accidental, though this is frequently the case. 



The morphological and cultural peculiarities of bacillus 

 coli are as follows : 



