68 VARIATIONS IN FERMENTING POWER [ch. v 



another by "plating out" a mixed culture on the appropriate 

 medium. 



It is this that constitutes the real value of the "sugar 

 reactions." In other words the, tests are of more use for 

 purposes of identiJiGation than of classification. 



How far is this conclusion borne out by a study of the 

 relation between fermentation tests and agglutination re- 

 actions ? 



In some cases, alteration in fermenting powers is not 

 accompanied by any disturbance in the agglutination pro- 

 perties, which remain constant. 



For example, Twort and Penfold have both shown that the 

 altered fermenting power on the part of B. typhosus towards 

 lactose is not accompanied by any alteration in agglutination 

 properties. The organism described by Klotz as differing from 

 B. typhosus in its capacity to ferment lactose and saccharose, 

 and in other characters, nevertheless was agglutinated by 

 typhoid serum in high dilutions. 



Bahr, in describing the altered fermenting power of dy- 

 sentery bacilli, following transmission through the intestine of 

 the fly, states that the variants displayed no alteration in 

 agglutination properties. Lentz mentions a "Flexner" strain 

 which after seven years' laboratory cultivation lost its power to 

 ferment maltose but still retained its agglutination properties 

 unchanged. 



In other cases, alteration in fermentingpowersis associated 

 with loss of agglutination properties. For example, Wilson, 

 in describing an organism isolated from the urine of a "typhoid 

 carrier" and considered by him to be a derivative of B. typho- 

 sus, states that not only were the fermenting properties altered 

 but the agglutination tests no longer corresponded with those 

 of B. typhosus. Penfold found that colonies of B. typhosus 

 which had lost the property of fermenting glycerine, showed 

 impaired agglutinability also, though typical fermenting 

 colonies on the same plate were normal as regards agglutina- 

 tion. 



Horrocks observed that a strain of B. typhosus derived 

 from the urine of a carrier, when grown in the diluted filtered 



