170 



The Philippine Journal of Science 



1916 



are of more or less interest and importance, for while with 

 some organisms fermentation is so active and definite that results 

 are clear-cut under usual conditions, others, among which B. 

 pestis is to be included, are less active in this respect and are, 

 therefore, prone to irregularities of result unless the conditions 

 of experiment are properly controlled. 



Different types of media necessarily present different condi- 

 tions, such as essential suitability, aeration, availability of con- 

 tained reagent, and diffusion of end product, all of which may 

 affect the metabolism of the organism under consideration. Be- 

 side these, differences in indicators must also be considered. 

 In order to demonstrate the influences of certain of these various 

 factors, a considerable number of tests have been carried out. 



THE INFLUENCE OF TYPE MEDIUM ON FERMENTATION 



The tests described above demonstrate that for B. pestis, 

 which in most instances is a weak fermenter, the nature of the 

 medium used plays an important role. Comparison of the num- 

 bers of sugars fermented in each type emphasizes the superiority 

 of bouillon, as has repeatedly been shown for other organisms. 

 Litmus-agar slants under certain conditions are almost as useful, 

 but Hiss's serum water is of much less value, and the results with 

 it are more misleading. These comparisons are summarized 

 in Table IV, which is compiled from the results already shown 

 together with certain reactions yet to be discussed. 



Table IV. — Summary of carbohydrate fermentation by B. pestis in various 

 media, with 0.5 and 1 per cent concentration of sugars. 



[Symbols indicating degree of acid production: ++ = strong and constant; + = definite and 

 usual; ± = weak and irregular but usual; + = unusual and weak; — =none.] 



Medium. 



Dextrose . 

 Mannite . 

 Levulose - 

 Maltose.. 

 Arabinose 

 Galactose. 



Salicin 



Glycerin . 

 Dextrin . . 



Litmus serum- 

 waters. 



Litmus 



agars. 



Bouillon 

 (titrations). 



0.5 per 

 cent 



1.0 per 

 cent 



0.5 per 

 cent 



1.0 per 

 cent 



0.5 per 

 cent 



1.0 per 

 cent 



sugars. 



sugars. 



sugars. 



sugars. 



sugars. 



sugars. 



+ + 





+ + 





+ + 





+ + 





-i-l- 





+ + 





± 



+ 



+ 





+ + 





T 



+ 



± 



■+ 



+ + 



+ + 



(+?) 



+ 



- 



+ 



+ 



+ 



— 



=F 







± 



+ 



+ 



— 



± 



— 



+ 



+ 



+ 



— 



— 



T 



+ 



+ 



T 



— 



— 



— 





(±?) 



(±?) 



Remarks. 



Strong. 



Do. 



Do. 

 Moderate. 

 Weak. 



Do. 



Do. 

 Irregular. 

 Negative. 



Tests with the following were clearly negative : Lactose, adonite, inosite, saccharose, dulcite, 

 sorbite, rafiinose, amygdalin, nutrose, and inulin. 



