BY R. GREIG SMITH. 



233 



The Influence of different Carbonaceous and Nitrogenous 

 Constituents. 



The most pronounced result is the small yields of the peptone 

 media as compared with the amides, asparagine and urea. 

 Asparagine is the better amide, and it is in all probability the 

 form in which the bacterium obtains its nitrogen under natural 

 €onditions. At the same time it must be remembered that the 

 bacteria under experiment had been subcultivated upon potato- 

 extract agar, to the asparagine of which the bacteria must have 

 become accustomed under artificial conditions. 



The isolation of a fresh race of the hacterium, — The accustom- 

 ing to certain nutrients by subcultivation upon certain media 

 must be borne in mind when discussing the nutrition of the 

 bacteria. We have seen that certain carbohydrates are more 

 favourable to slime-formation than others, but the same results 

 might not have been obtained had the organisms been taken 

 directly from their natural habitat and sown upon the experi- 

 mental medium. This is, of course, impossible, for the bacteria 

 must first be purified, and this process involves the employment 

 of artificial media. But much might be learned by minimisinfy 

 the time during which the bacteria are under the artificial con- 

 ditions. "With thia idea portions of the branches of a specimen 

 of Acacia decurrens were introduced into flasks containing a 

 saccharose-peptone medium. After some time a gummy mass 



* Tannin Q-l. potassium citrate Q-l, (sugars, etc. 2-0), (asparagine O'l, peptone 0-1 

 urea 0-033), agar 2-0, water 100. v t- s , t- f , 



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