228 BACTERIOLOGICAL EXAMINATION OF WATEtt. 



proportion of 1-50, 1-100, 1-200, 1-500, 1-1000. The experi- 

 mental investigation of the 150 cultures of B. coli extended 

 over a period of four months, consequently it was necessary to 

 employ different batches of anti-typhoid serum ; and to make the 

 results strictly comparable, the various specimens of serum were 

 standardised week by week with two stock cultures of B. typhosus. 

 All through the experiments the sera used gave a complete 

 agglutination in a dilution of 1-1000 and a marked reaction in 

 a dilution of 1-10,000 with the stock cultures of B. typhosus. 

 The results obtained with the 80 cultures of B. coli isolated 

 from enteric stools are shown in the following table : 



TABLE A. 



VARIETIES OF B. COLI FEOM ENTERIC STOOLS TESTED 

 WITH ANTI-TYPHOID SERUM. 



