QUALITATIVE BACTERIOLOGICAL ANALYSIS. 251) 



with urine, faeces and refuse from manufacturing processes, may 

 contain sodium chloride and sodium sulphide, and so present 

 conditions favourable to the duration of life of cholera vibrios, 

 Trenkmann's experiments certainly explain the prolonged 

 vitality of the cholera vibrios in certain epidemics, such as 

 that at Hamburg, where the water was distinctly saline 

 owing to the high percentage of salt discharged from salt 

 works into the Elbe. 



Summarising the results of the various experiments which 

 have been made on the vitality of cholera spirilla, Tiemann 

 and Gartner give the following conclusions : " Cholera spirilla 

 behave very differently in water. Most commonly they dis- 

 appear in a few days ; at C. they can exist for several days, 

 at 10 C. for weeks,' and at 20 C. for months." The rapid dis- 

 appearance of cholera spirilla from an infected water cannot be 

 safely assumed, as most of the earlier experiments which appeared 

 to demonstrate this point were made without attempting to 

 isolate the spirilla by the special methods now in use. Gruber, 

 employing special methods, has shown that when cholera spirilla 

 are mixed with putrefactive bacteria, although the latter may 

 gain the ascendency for some time, yet the vitality of the former 

 is not extinguished, for if the struggle between the two be suffi- 

 ciently prolonged, the presence of the cholera bacilli may be again 

 demonstrated by cultivation. 



The vitality of cholera spirilla in water containing carbonic 

 acid gas is an important practical question. Hochstetter has 

 studied this subject with great care. In eight experimenls with 

 fifty-six flasks of soda-water, he found that the cholera spirilla 

 could be isolated in a living state after three hours exposure to 

 the influence of carbonic acid gas, but after twenty-four hours 

 not a single spirillum could be detected. The rapid disappear- 

 ance of the spirilla was found to be due to the carbonic acid gas 

 and not to the chemical constituents of the water. In soda- 

 water which had been heated so as to drive off* the carbonic acid 

 gas cholera spirilla were found alive up to the eighteenth day. 

 A pressure of two atmospheres appeared to have little influence 

 in destroying cholera spirilla ; carbonic acid gas simply passed 

 through the water killed the spirilla in the shortest time. 



The vitality of the cholera bacillus in crude sewage has quite 



