SURVIVAL OF THE COMMA BACILLUS 437 



In some experiments by Dempster 1 it was found that 

 the comma bacillus lived from three to five days in dry 

 soil, but only one day in an artificially dried soil, while 

 in moist soil it lived from twenty- eight to sixty-eight days. 

 In peat, however, it was invariably dead within twenty- 

 four hours. In sterilised salt solution (0-75 per cent.) the 

 comma bacilli were alive on the 159th day, and in fresh 

 urine (sterilised) they lived fourteen days at 37 C. and 

 twenty-nine days at 22 C. 



In sterilised distilled water the cholera vibrio usually 

 rapidly dies, as a rule within twenty-four hours. The 

 addition of sodium chloride greatly increases the length of 

 time it may remain alive, a survival of five or six weeks 

 having been recorded. In ordinary sterilised potable 

 waters it may survive many months. In unsterilised 

 potable waters its survival is greatly influenced by the 

 presence of salts ; in some cases it dies out rapidly ; in 

 others, especially in those containing a large proportion 

 of salts, it may remain alive for some time. Houston 2 

 found that cholera vibrios die very rapidly in raw Thames, 

 Lee, and New River waters as the result of storage in the 

 laboratory. At least 99-9 per cent, perish within one 

 week, and it was not possible to isolate any, even from 

 100 c.c. of the water, three weeks after infection. Klein 3 

 found that the cholera vibrio could retain its vitality for 

 at least fourteen days in unsterilised sea- water, while 

 from the interior of oysters, kept in water infected with 

 the vibrios, it was obtained up to nine days after infection. 

 In sterilised sewage the cholera vibrio multiplies and 

 survives for months ; in unsterilised sewage it may survive 

 for two to four weeks (Houston). 



Pathogenicity. The disease is spread mainly by infected 



1 Med.-Chir. Trans., vol. Ixxvii, 1894, p. 263. 



2 Metropolitan Water Board, Fifth Rep. on Research u-o)k, 1910. 



3 Rep. Med. Off. Loc. Gov. Board for 1896, p. 135. 



