ISOLATION OF V. CHOLERA 723 



and Mackie's method and subsequent plating. In all 

 cases the organism isolated must be examined as to its 

 morphological, cultural, and biological characters, and 

 should have its agglutination reaction tested with a high- 

 grade typhoid serum. Two organisms which are likely 

 to be mistaken for the B. typhosus, unless all tests are 

 applied to them, are the B. (fcecalis) alkaligenes (p. 438) 

 and B. (aquatilis) sulcatus. Both occur in the dejecta 

 and in polluted water, and are like the B. typhosus in 

 morphology, but neither agglutinates with typhoid serum. 

 The B. sulcatus hardly grows at 37 C. and is almost 

 a strict aerobe. Some varieties of typical and of atypical 

 B. coli tend to agglutinate with typhoid serum, so the 

 agglutination reaction must be carried out quantitatively. 



THE ISOLATION OF THE CHOLERA VIBRIO FROM WATER. In 

 the examination of suspected water supplies, the best method to 

 employ for the detection of the cholera vibrio is to take advantage 

 of the fact, first noted by Dunham, that the cholera vibrio multi- 

 plies with great rapidity in alkaline saline peptone solution. The 

 suspected water is examined as follows : 90 c.c. of the water are 

 introduced into each of six Erlenmeyer flasks, and 10 c.c. of a 

 sterile, slightly alkaline solution containing 10 per cent, of pep- 

 tone and of sodium chloride are added to each flask, thus con- 

 verting each mixture into 1 per cent, peptone and salt. The 

 flasks should be of such a size that the fluid is not more than one 

 inch deep. The flasks are loosely capped with caps of filter-paper, 

 and incubated at 37 C. The subsequent procedure is the same 

 as that described in No. 2, p. 540. 



STERILISATION OF WATER. This may be done on the small 

 scale by heat, by the use of germicidal agents, or by filtration 

 through a filter (see p. 725). Heat may be applied by simple 

 boiling, or by the use of apparatus in which the water is heated 

 to 65-90 C., and the outgoing hot water is cooled by the ingoing 

 cold water, which itself is thus warmed, thereby effecting economy 

 in fuel (Griffiths' and other sterilisers). The chemical germicides 

 that have been employed are (1) sodium bisulphate, 15 grains to 

 the pint ; (2) potassium permanganate, sufficient to tinge the 



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