252 Proceedings of Indiana Academy of Science 



TABLE 12. 24 Hour Growth. .1 Per cent Xylose. 



Summarizing- these tables it will be found that all three indicators 

 may be used in media for the detection of acid. Phenol red is the most 

 sensitive, as might be expected, then brom thymol blue and finally brom 

 cresol purple. The last two proved very satisfactory and could almost 

 be used interchangeably. The amount of acid produced is the determin- 

 ing factor in each case so that we might expect different results with 

 different indicators. For example, typhoid and dysentery may be differ- 

 entiated by their action on arabinose with brom thymol blue but not 

 with brom cresol purple. Not enough acid has been produced to bring- 

 about a change with brom cresol purple. On the other hand, these same 

 organisms may be differentiated by their action on mannose and galac- 

 tose with brom cresol purple but not with brom thymol blue. In this 

 case the action has gone too far to be detected with brom thymol blue. 



All the sugars used were fermented by one or more organisms. 

 Three of these, dulcitol, raffinose and sucrose were fermented with very 

 little or no gas .so that for this purpose they are of little or no use. 



Arabinose will divide the group into four parts. Colon, typhoid 

 and dysentery stand out by themselves while para A., para B., and 

 tnteritidus remain undifferentiated. 



Dextrose is the most easily fermented of all the sugars used. 

 Typhoid, dysentery and enteritidus stand out as distinct individuals 

 while the other three show no difference in their reactions. 



Galactose breaks up the group into five parts, para B. and enteriti- 

 dus in one group and the other four as separate individuals. 



Lactose is fermented only by colon. 



Levulose gives different reactions for typhoid, dysentery, and para 

 A. while the same reaction is given for colon, para B. and enteritidus. 



Maltose is fermented by typhoid but not by dysentery, thereby dis- 

 tinguishing between these two. The others all give like reactions. 



Like maltose, mannose will .separate typhoid and dysentery but will 

 further divide the remaining four into three groups, colon and enteri- 

 tidus as separate individuals and the other two undifferentiated. 



Rhamno.se will distinguish between colon, para A., para B., and 

 enteritidus. Typhoid and dysentery are undifferentiated. 



Xylose gives one reaction for colon, para B. and enteritidus and 

 another for typhoid, dysentery and para A. 



