438 BACTERIOLOGY. 



Select a culture in which the vacuolations are quite 

 marked. Examine this culture unstained. Do the 

 organisms look as if they contained spores? How 

 would you demonstrate that the vacuolations are not 

 spores ? What is the crucial test for spores ? 



Obtain from normal faeces a pure culture of the com- 

 monest organism present. Write a full description of 

 it. Now make parallel cultures of this organism and 

 of the typhoid bacillus on all the different media ? How 

 do they differ ? In what respects are they similar ? 



BACILLUS COLI (ESCHERICH), MIGULA, 1900. 



Synonyms: Neapeler bacillus, Emmerich, 1884; Bacillus pyogenes 

 foetidus, Passet, 1885; Emmerich's bacillus, Eisenberg, 1886; Bac- 

 terium coli commune, Escherich, 1886. 



This organism was discovered by Escherich, in 1886, 

 in the intestinal discharges of milk-fed infants. It has 

 since been demonstrated to be a constant inhabitant of 

 the intestines of man and domestic animals, and is, 

 therefore, considered a commensal species. 



For a time after its discovery it was considered of 

 but little importance and attracted attention only be- 

 cause of its resemblance, in certain respects, to the bacil- 

 lus 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 knowledge 

 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 ap- 

 proach one another in some of their biological peculiar- 

 ities is true ; but, as we shall learn, they each possess 



