THE VITAL CONDITIONS OF BACTERIA. 87 



NOT AT ALL. 



Bacillus tetani I Bacterium erysipelatos suura. 



Bacterium murisepticum. I Bacterium cuniculicida. 



The addition of the other substances recommended 

 by Uschinsky did not cause vigorous growth of other 

 varieties (such as diphtheria and tetanus), while on 

 the addition of three to four per cent glycerin the 

 medium becomes very serviceable even for the tubercle 

 bacillus. 



Although cultures in the simple nutrient media just 

 described possess great theoretical interest, they are 

 used very little for purposes of differential diagnosis. 



Much more frequent use is made of flesh-water pep- 

 tone gelatin, flesh-water peptone agar, bouillon (with 

 or without the addition of grape sugar or milk sugar), 

 glycerin agar, milk, potato discs. 



We must always have these on hand, because no 

 differential diagnosis is possible without them, and 

 no variety can be properly described which has not 

 been tested in regard to its condition in all these nu- 

 trient media (with the exception of glycerin agar). 



Less use is made of the following nutrient media : 

 potato water, lamb bouillon, blood serum (fluid and 

 firm), serum agar, agar smeared with blood, meat, 

 pieces of bread, mashed potatoes, rice, boiled or raw 

 eggs. 



2. REACTION OF THE NUTRIENT MEDIA. 



As has been remarked above, the large majority of 

 bacteria, especially the pathogenic forms, have a 

 predilection for neutral or feebly alkaline nutrient 



