WATER 431 



III. The Eberth Group. 



B. typhosus. 

 B. dysenteriae (Shiga). 

 B. dysenteriae (Flexner). 

 B. faecalis alcaligines. 



18. Confirm these results by testing the organisms 

 isolated against specific agglutinating sera obtained 

 from experimentally inoculated animals. 



If a positive result is obtained when using this 

 method, it only needs a simple calculation to determine 

 the smallest quantity (down to o.i c.c.) of the sample 

 that contains at least one of the microbes of indication. 

 For instance, if growth occurs in all the tubes from 4 to 

 10, and that growth is subsequently proved to be due 

 to the multiplication of B. coli, then it follows that at 

 least one colon bacillus is present in every 10 c.c. of the 

 water sample, but not in every 5 c.c. If, on the other 

 hand, the presence of the B. coli can only be proved 

 in flask No. 7, then the average number of colon bacilli 

 present in the sample is at least one in every 50 c. c. 

 (i. e., twenty per litre), but not one in every 25 c. c. and 

 so on. 



The general outline of the method of identifying 

 the members of the coli-typhoid group is given in the 

 form of an analytical schema whilst the full differen- 

 tial details are set out in tabular form. 



