94 Elements of Water Bacteriology. 



waters by cutting out at once organisms other than B. 

 coli which fail to grow at this high temperature. Chris- 

 tian (1905), Neumann (1906), and Thomann (1907) 

 have reported good results by the use of this method. 

 It remains, however, to be demonstrated that high tem- 

 peratures do not inhibit colon bacilli in slightly polluted 

 waters. Nowack (1907) found that laboratory cultures 

 of B. coli often fail to produce gas in Eijkman's medium 

 at 46 degrees, unless large numbers are introduced. With 

 some strains an inoculation of over a million bacteria was 

 necessary to cause gas formation. 



It appears on the whole that the safest method at present 

 available is the dextrose broth enrichment process which 

 alone rests on the sure basis of a great number of observed 

 coincidences between sanitary inspection and bacteriolog- 

 ical examination. 



When it is desired to examine samples larger than i c.c. 

 for B. coli it becomes necessary to modify the enrichment 

 process by adding the nutrient material to the water 

 instead of the reverse. For this purpose phenol-dextrose 

 broth (consisting of broth with 10 per cent dextrose, 5 

 per cent peptone, and .25 per cent phenol) may be added 

 to the sample of water to be enriched as suggested by Gage 

 (Gage, 1901). Generally 10 c.c. of the broth is added to 

 100 c.c. of the water. The sample is then incubated at 

 37 degrees for twenty-four hours, and if at the end of that 

 time growth has taken place, a cubic centimeter is inocu- 

 lated into a dextrose tube. If this tube shows gas 



