OTHER INTESTINAL BACTERIA 



205 



rapidly. The streptococci first became apparent after 

 lo to 15 hours and reached their maximum after 20 to 

 60 hours, according to the number originally present. 

 Applying the same method to polluted waters, similar 

 periodic changes were observ'ed; nearly pure cultures 

 of B. coU were first obtained, then the gradual displace- 

 ment of one form by the other took place, and at length 



RELATIVE GROWTH OF B. COLI AND SEWAGE STREPTO- 

 COCCI FROM POLLUTED WATERS IN DEXTROSE BROTH 



(Prescott and Baker, 1904) 



the streptococci were present either in pure culture 

 or in great predominance as shown by the accompany- 

 ing tables. The samples of water were plated directly 

 upon Utmus lactose agar and the plates were incubated 

 at 37° for 24 hours, when the red colonies were counted. 

 At the time of plating, i c.c. from each sample was also 

 inoculated into dextrose broth in fermentation tubes, 



