IX 



TABLE XVI. (Normal bouillon). 



When 3% lactose neutral red bouillon (Table XIV) 

 is used, the reaction takes place in the following way: 

 B. typhosus gradually changes the colour of the medium 

 to yellow, passing through the stages of red, orange red 

 and orange. The ultimate yellow colour is retained for 

 months. 



B. coli, on the other hand, changes the colour to 

 red even if the medium is alkaline, and though it may 

 produce decoloration during the first few days in 

 the acid and neutral media, a red colour is gradually 

 regained and an ultimate shade of magenta is obtained 

 and preserved unaltered. The reaction, as modified 

 by us, has the disadvantage, that it does not occur until 

 between the 4th 6th day, otherwise there is much to 

 be gained by its use as: 



