92 ELEMENTS OF WATER BACTERIOLOGY. 



POLLUTED WATERS. 



i c.c. 100 c.c. 



Samples examined 50 48 



Dextrose broth positive 50 37 



Lactose plate positive 50 26 



Colon group 18 4 



Paracolon group 6 



Streptococcus group 25 22 



B. cloacae i 



The authors pointed out that these tables indicate 

 that bacteria capable of growth at the body temperature 

 and fermenting dextrose and lactose are infrequently found 

 in unpolluted waters, and colon bacilli are very rarely 

 present^ since in 157 samples typical colon bacilli only 

 appeared 5 times. In the polluted waters it is evident 

 that colon bacilli originally present were in many cases 

 killed out during the process of enrichment by the strep- 

 tococci, since every one of the dextrose-broth tubes showed 

 gas at the first incubation of i c.c. 



The latest important contribution to this subject conies 

 from Dantzic. Petruschky and Pusch (Petruschky and 

 Pusch, 1903) examined a considerable series of waters 

 from different sources by incubating measured samples 

 with equal amounts of nutrient broth and isolating upon 

 agar. In 45 samples of well-waters they found B. coli 

 7 times in .01 c.c., 9 times in .1 c.c., and 7 times in i c.c. 

 In the other 22 cases it could not be found in i c.c. and in 

 4 cases not in 100 c.c. One sample showed it only in .600 

 c.c. and i not in 750 c.c. Of 29 river- waters, only 2 failed 

 to give positive results in .1 c.c. and 14 showed B. coli in 

 ,001 of a c.c. or less. In sewage the number varied from 



