138 ELEMENTS OF WATER BACTERIOLOGY 



is distinctly ambiguous. In one section of the report 

 " Recommended Procedures for Treating Samples " 

 complete isolation and the use of the old confirmatory 

 tests in fermentation tubes, milk, gelatin tube, peptone 

 solution and nitrate broth are discussed. In another 

 place it is pointed out that the entire colon group is 

 typical of the presence of faecal matter and the follow- 

 ing " Quantitative Test for the B. coli Group " is 

 recommended : 



" Add the quantities of water or sewage to be tested 

 in dilutions by tenths, sufficient in number to obtain 

 a negative test, to fermentation tubes holding at least 

 40 c.c. of lactose bile, incubate at 37 C. and note 

 the production of gas. Gas often forms in a few hours 

 when large numbers of B. coli are present, but the 

 standard time for observing gas production is 48 hours. 

 Small numbers of somewhat attenuated B. coli may 

 require 3 days to form gas. Attenuated B. coli does 

 not represent recent contamination and all B. coli 

 not attenuated grows readily in lactose bile. No 

 other organism except B. welchii gives such a test in 

 lactose bile. B. welchii is of rather rare occurrence 

 in water, is of faecal origin, is almost invariably accom- 

 panied by B. coli, and while the sanitary significance 

 is the same it may if desired be distinguished from B. 

 coli by a microscopical examination of the bile solution 

 when long strings of much larger bacilli than B. coli 

 are seen." 



So far as we can judge from the report this appears 

 to constitute the preferred procedure of the Committee. 

 In any case the matter was passed upon by the Labora- 



