256 BACTERIOLOGICAL EXAMINATION OF WATER. 



alive after twenty to sixty days ; he considered that the presence 

 of common salt exercised a favourable influence on the vitality 

 of the spirilla. Hochstetter detected cholera spirilla in steri- 

 lised Berlin tap-water, kept at 30 C., after three hundred and 

 ninetv-two days ; although in some cases the water was found 

 not to be sterile, other organisms having gained access to it, 

 owing to the length of time covered by the experiment. The 

 temperature at which the vibrios are kept seems to influence 

 the result. In some experiments the spirilla appeared to live 

 longer at a temperature of 16 C. than at a temperature of 11 C., 

 which corresponds to that usually found in well-waters. At 

 Altona, however, Koch found that cholera vibrios rapidly 

 disappeared from the water in a well, but in a litre of the same 

 water, removed from the well and kept at 3 to 5 C., he de- 

 tected the vibrios after eighteen days. Uffelmann, working 

 with a very impure harbour-water from Rostock, found cholera 

 vibrios at a room temperature only up to the third day. 

 These experiments, which are in harmony with the outbreaks 

 of cholera at Nietleben and Altona in winter, show that 

 cholera spirilla live longer in cold than warm water ; probably 

 because they are not crowded out by the water organisms which 

 cannot multiply at a low temperature. The observations at 

 Nietleben also showed that cholera vibrios could exist in ice- 

 cold water under snow and ice. Uffelmann allowed water 

 containing cholera vibrios to freeze, and every day melted just 

 as much of the ice as he required for his experiments. Al- 

 though the temperature at night fell to 24'8 C., living cholera 

 spirilla were isolated from the melted ice-water up to the fifth 

 day. Trenkmann made some remarkable experiments on the 

 influence of salts on the growth of cholera spirilla. Test tubes 

 were carefully cleaned and filled with 10 c.c. of a well-water ; then 

 into each tube one, two, or three drops (25-27 drops = 1 gramme) 

 of a 10 per cent, solution of sodium chloride, sodium nitrite, 

 sodium nitrate, sodium carbonate, and di-sodium phosphate 

 were added by means of a small pipette. The test-tubes were 

 sterilised, and then each of them inoculated with one loopful of 

 a twenty-four hours broth culture of the cholera spirillum. 

 The inoculated glasses were kept at 21-24 C., and after 

 twenty-four hours a loopful was taken from each of them with 



