XI, B. 4 



Wade: Carbohydrate Fermentation 



173 



cultures, it seems that fermentation in the peptone media was 

 usually rather more active than in the corresponding bouillon. 

 Of interest, however, is the fact that salicin fermentation in 

 peptone water is remarkably depressed, this being similar to 

 the results obtained in serum water. The uniformity in the 

 amount of acid formed in the same medium by the different 

 strains is again well shown. There is sometimes, however, a 

 distinct difference in the end reaction in the different sugars, an 

 indication, possibly, of different end products which are inhibit- 

 ory in different concentrations. 



Influence of primary acidity on end reaction. — In connection 

 with inhibition of fermentation the question arises whether a 

 simple primary acidity, due to a known substance, might not 

 be tolerated to a higher degree than the mixed products of 

 bacterial metabolism. To investigate this point, two series of 

 cultures of different reactions were made by adding hydrochloric 

 and lactic acids to neutral broth. Dextrose and mannite were 

 again used for the carbohydrates. The results of these titrations 

 indicated that fermentation is inhibited as quickly by hydro- 

 chloric or lactic acid as by the products of the organism's own 

 metabolism. No difference whatever was demonstrated in the 

 tolerance to the two acids. 



Acid limit with meat-infusion broths. — In the foregoing titra- 

 tions the maximal acidity attained was between 2.5 and 3 per 

 cent to phenolphthalein. This is not the highest total acidity 

 tolerable- to B. pestis, for cultures in sugar broths made up of 

 sugar-free veal infusion attain a considerably higher acidity 

 than has been the case in beef-extract broths under any 

 circumstance. 



Table VII. — Final reactions attained in 1 per cent veal-infusion sugar 



broths. 



strain. 



Dextrose. 



Mannite. 



Maltose. 



A - 



4.0 

 4.1 

 4.2 

 4.2 

 4.2 

 3.8 

 4.2 

 3.8 

 4.0 

 4.0 



1.6 

 1.3 



4.2 

 4.0 

 4.2 

 4.1 

 3.8 

 3.8 

 4.1 

 4.1 

 3.5 

 4.3 



LB 

 L3 



3.5 

 4.2 

 2.2 

 4.0 

 3.7 

 4.0 

 3.6 

 3.8 

 3.7 

 2.1 



1.7 

 1.7 



B - _ 



C - ..... 



D . ... 



E . 



p ... 



G 



H 



I 



J 



Control titrations: 



1 



2 





