IX 



H 2 S0 4 the yellow colour does not appear until after 2 

 days and then, only in the upper half of the medium. 

 This is a contradiction to the statements of Rothberger 

 and Scheffler, who maintain that the colour change, 

 takingplace in themedium,neverreachesthe upper V 2 Ctm. 



Thus it is obvious, that the results, obtained in either 

 bouillon or agar, are dependent upon just the same 

 factors, though in the latter medium the differences 

 are not so striking. This is quite in accordance with 

 our view, that the reaction, if it occurs at all, is best 

 marked in bouillon. 



In Table IX, where a stab culture was used, the appear- 

 ance of the reaction was both slower and less certain 

 than with a shake culture. Therefore the use of the 

 latter is to be preferred if agar is employed as the me- 

 dium. The results with stab cultures however show 



17 



