CH. v] VARIATIONS IN FERMENTING POWER 69 



urine of a second " typhoid carrier," was deprived not only of 

 its power to ferment but also its property of agglutinating in 

 the presence of typhoid serum. 



Thir dly,classi^ations according to/ermenting powers and 

 according to agglutination properties give altogether different 

 results. 



Ohno (1906), in his elaborate investigations on 74 strains 

 of dysentery derived from different sources, found that a 

 classification based on their different powers of fermentation 

 did not correspond with a classification according to their 

 agglutination reactions. Torrey describes dysentery bacilli 

 possessing different fermenting properties but giving the same 

 agglutination reactions. The pneumococcus is distinguished 

 fi'om other members of the streptococcus group by its different 

 fermenting properties, particularly with reference to inulin ; 

 nevertheless the pneumococcus and other streptococci tend to 

 originate common group agglutinins. 



It would appear therefore that the power of producing 

 fermentation bears no relation to agglutinability, and in the 

 final resort, if reliance is to be placed, for purposes of classifica- 

 tion, on one test the other must necessarily be discredited. 

 As regards identification, however, there is this to be said — 

 organisms immediately after their isolation from the tissues 

 or excretions are, as a rule, more typical in their fermenting 

 properties than the same organisms after even a short period 

 on artificial media, whereas the reverse fi-equently holds true 

 as regards their agglutination reactions. In deciding, there- 

 fore, which of the two series of tests is to be relied upon in 

 cases where they conflict, the length of the period of cultivation 

 is of great importance ; the fermentation tests will be found 

 most reliable in the identification of an organism in those 

 cases where agglutination tests are least so. 



It is seen then that the fermentation tests, though for 

 purposes of classification they may prove at variance with 

 the agglutination reactions, as a means of identification may 

 supplement the latter. 



