206 ELEMENTS OF WATER BACTERIOLOGY 



which were Hkewise incubated at 37°. After various 

 periods, as indicated by the tables below, the tubes 

 were shaken thoroughly and i c.c. of the contents 

 withdrawn. This was diluted (generally 1-1,000,000,) 

 with sterile water, plated on litmus lactose agar in the 

 usual way, and incubated for 24 hours. The colonies 

 of B. coli and streptococci were distinguished micro- 



RELATIVE GROWTH OF B. COLI AND SEWAGE STREPTO- 

 COCCI FROM POLLUTED WATERS IN DEXTROSE BROTH 



(Prescott and Baker, 1904) 



scopically, and by difference in color and general 

 characters. 



The successive growth of these two intestinal groups 

 in the same dextrose-broth tube suggests the following 

 method for the detection of both B. coli and sewage 

 streptococci. 



Inoculate the desired quantity of water, preferably 



