532 A MANUAL OF BACTERIOLOGY 



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 ! 

 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 2 

 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). 



The disease is spread mainly by infected water ; milk, 

 salads, vegetables, and flies are other sources of infection. 

 The organism has been found in the dejecta of contacts 

 not suffering from the disease, and it may sometimes 

 persist for long periods after convalescence. In these 

 cases the vibrio may sometimes be located in the biliary 

 tract. Crendiropoulo examined the stools of 34,461 

 persons on ships coming from cholera-infected ports. 

 Cultures of vibrios were obtained from sixty-three of 

 these, of which twenty-three were agglutinated, and forty 

 were not agglutinated, by a high-titre cholera serum. 



Paihogenicity . The causal relation of the cholera 

 vibrio to the disease has been doubted in the past, but 

 the voluminous researches which have since been made 



1 Metropolitan Water Board, Fifth Rep. on Research Work, 1910. 

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



