114 EXAMINATION OF AIR AND WATER 



collected on the candle to 5 or 10 c.c. of sterile water. This is 

 now a concentration or emulsion of the organismal content of 

 the litre of water, and may be used for examination for special 

 organisms. 



{a) Place 0-5 or i c.c. of the concentrated emulsion in each of 

 three tubes of 10-15 c.c. of fresh sterilised milk. Put the three tubes 

 into the water bath for fifteen minutes at 80° C, and after allowing 

 them to cool place them in a Buchner's tube or cylinder contain- 

 ing pyrogallic solution (Pyrogallic acid, 120 grains, strong liquor 

 potassae, 10 c.c). Accurately seal up the Buchner, and place it, 

 containing the tubes, in the incubator at 37° C, The next day, or 

 in thirty-six hours, examine for B. enteritidis sporogenes. If that 

 organism is present the following characteristic appearances will 

 be apparent (Klein). The cream of the milk will be torn and 

 altogether dissociated by the development of gas, so that the 

 surface of the medium becomes covered with stringy white masses 

 of coagulated casein enclosing a number of gas bubbles. The 

 main portion of the tube formerly occupied by the milk will 

 contain a colourless, thin, watery whey, with a few lumps of casein 

 adhering here and there to the sides of the tube. If the tube be 

 opened there will be found to be a smell of butyric acid and an 

 acid reaction. If some of the contents of the tube are stained, as 

 slide preparations, the bacilli will be seen. 



{b) Take from o-i to 0-5 of the concentrated emulsion and add to 

 three tubes of phenolated gelatine and make plates as in the 

 quantitative examination. Colonies developing in these plates 

 should be suspected of being B. coli communis and tested accord- 

 ingly ; or, inoculate from the concentrated water three tubes of 

 Parietti's broth, and incubate at 'i,'j° C. Those tubes which show 

 growth in one to three days should be plated out on ordinary 

 or phenolated gelatine and colonies of B. coli examined for. 

 Some authorities recommend incubating Parietti's tubes at 42° C, 

 a temperature favourable to B. coli but unfavourable to ordinary 

 water organisms. Tubes of glucose formate bouillon may also be 

 inoculated with o- 1 to 0-5 c.c. of the concentrated emulsion and incu- 

 bated in a Buchner's tube at 42° C. and all the tubes which show 

 turbidity in twenty-four hours may be plated out on gelatine or 

 alkaline glucose litmus agar and the B. coli, if present, thus isolated. 



Subcultures should be made in gelatine or glucose gelatine (for 

 gas production), milk (for acidity and coagulation), and peptone 

 water (for indol). 



