IX 



while B. coli and the 3 bacilli of the coli group produce 

 a magenta red colour. In column 0.5 and 1 H 2 S0 4 a yellow 

 colour is produced by Ty. and 49b of the typhoid group, 

 but it is seen on the other hand that Sv.18, the second 

 member of the typhoid group, keeps the red colour just 

 in the same way as B. coli and the 3 members of the 

 coli group. Thus we have also here a strong proof of 

 the importance of estimating the quantity of free acid 

 if a neutral red medium is used for differentiating these 

 groups, though it may be of much less consequence in 

 of 3 / lactose than in a '/ 2 % glucose medium. 



From Table XXIII it will be seen that the different va- 

 rieties of the typhoid or coli group, whether they are 



35 



