410 



PATHOGENIC MICROORGANISMS 



selves use largely the Endo fuchsin-agar or Kendall's modified Endo 

 medium. (See p. 135.) Emulsions of feces are made in tubes of 

 ordinary broth or salt solution and smears of this emulsion are made 

 upon several large plates of the fuchsin-agar by means of a glass smearing 

 rod. The colonies of Bacillus coli, after eighteen or more hours of 

 incubation, will be found to have brought back a, deep red color to the 

 medium, whereas the typhoid colonies are small, more transparent, and 

 have left the medium uncolored. 



An excellent medium recently devised is that of Krumwiede. (See 

 p. 136.) 



In all cases where plates are prepared from broth emulsions of feces, 

 it is desirable t9 allow the emulsion to stand at incubator temperature 



FIG. 92. COLON AND TYPHOID COLONIES IN Hiss PLATE MEDIUM. (Planted 

 from stool. Note the small thread-forming typhoid colonies.) 



for an hour. Subsequent removal of fluid from the upper layers of the 

 medium is likely to bring away a comparatively larger number of the 

 organisms. 



The methods given above do not exhaust the records of work done 

 upon this problem. It is not satisfactory to compare any two methods 

 as to practical value, since all of them require familiarity with organisms 

 and media. In fact, it may be said that all of the methods given are 

 satisfactory if consistently employed by a worker who has become 

 thoroughly accustomed to the peculiarities of the typhoid colonies upon 

 the medium with which he is working. 



In all of these methods when suspicious colonies are found they are 

 identified morphologically and transplanted to such media as the Russell 

 double-sugar agar, or the Hiss tube medium. For rapid diagnosis 



