XI. B, 4 Wade: Carbohydrate Fermentation Yl^ 



similar to Hiss's in appearance and reaction. Its value, how- 

 ever, seems but moderately greater than the ordinary serum 

 water. With some sugars, as levulose and maltose, the reaction 

 in the peptonized cultures was considerably accelerated, but 

 with galactose the two media gave identical results, and with 

 salicin no fermentation occurred in either. 



SUMMARY AND DISCUSSION 



Cultivations carried out with ten strains of B. pestis in 

 media containing twenty fermentable substances have demon- 

 strated conclusively the fermentation activities of the organism. 

 Experiments have also demonstrated the parts played by certain 

 influencing factors in the results obtained. As shown in Table 

 IV, dextrose, mannite, and levulose are regularly and strongly 

 fermented, while maltose, arabinose, galactose, and salicin are 

 less constantly acted upon except in the more suitable media. 

 Glycerin, which Vourland and Schobl found to be fermented, in 

 my experience reacted with but three strains out of ten, and 

 then only under suitable conditions. This difference between the 

 strains seems to have no significance. Contrary to the conclu- 

 sion of MacConkey, dextrin is not fermented ; contrary, similarly, 

 to Schobl and to Vourland, saccharose remains untouched. 

 Salicin fermentation is peculiar in that it is practically negligible 

 in serum water and in simple peptone media, although positive 

 in agar and bouillons. 



The strains used included a culture isolated in 1912 from a 

 rat in New Orleans, three from human cases in the 1914 New 

 Orleans invasion (suggested at the time by the Federal author- 

 ities to have come from Liverpool), five isolated from cases 

 in the Philippine Islands, and one avirulent strain. Between 

 these there has been demonstrated no distinct difference except 

 for the irregularity with glycerin noted and except that between 

 the strains there are consistent although slight differences in 

 acid tolerance. This is shown numerically in Table III, where 

 the relative "activities" of the strains in bouillons have been 

 averaged. Strains G and H produce somewhat less, and strains 

 A and / slightly more, acid than the majority. These variations 

 are evidently not dependent upon length of time out of the 

 animal body. The relation to virulence has not been investigated, 

 but it is probably true that, as recently asserted by Berlin, 

 this feature, also, has no definite influence. 



There has been demonstrated a fairly constant point of max- 

 imum acid tolerance beyond which active metabolism as ex- 

 pressed in fermentation ceases. This is a well-recognized feature 



