96 ELEMENTS OF WATER BACTERIOLOGY 



demnation of a water-supply. The difficulty, however, 

 is that while non-acid-forming bacteria of this general 

 type are sometimes found in faeces, they are also 

 found in other habitats, and they are less abundant 

 proportionately, in polluted than in stored and safer 

 waters. If true dysentery and paratyphoid bacilli 

 can be isolated and identified by serum reactions it is, 

 of course, highly important. Houston' (1911), however, 

 has recently tested the method suggested by Starkey 

 (1906) for isolating these forms and found that it gave 

 negative results even with a water artificially infected 

 with about 14 typhoid bacilli and 21 Gartner bacilli 

 per c.c. In his own studies Houston reports that in 

 the examination of 13,442 microbes from polluted 

 river water he found only one member of the Gartner 

 group; and in another study of 20,771 colonies he 

 found only 2 typhoid-like forms. 



Isolation of the Cholera spirillum. The isolation of 

 the cholera spirillum from water can probably be accom- 

 plished with somewhat less difficulty than is encoun- 

 tered in the case of B. typhi. Schottelius (Schottelius, 

 1885) was the first to point out the necessity for grow- 

 ing this organism in an alkaline medium, and Loeffler 

 (Loeffler, 1893) found that its isolation from water 

 could be successfully accomplished by_adding 10 c.c. 

 of alkaline pepton broth to 200 c.c. of the infected 

 water and incubating for 24 hours at 37 degrees, when 

 the organism could be found at the surface of the 

 medium. 



Somewhat earlier than this Dunham (Dunham, 1887) 

 had made a special study of the chemical reactions of 



