258 BACTERIOLOGICAL EXAMINATION OF WATER. 



The following experiments were then made with unsterilised 

 water : 



Plate after twenty-four hours. 

 Cholera bucilli. Water bacteria. 



cent, sodium sulphide/ 



do. + do. do. + 2 drops do. 17,100 540 



do. + do. do. + 3 drops do. 28,100 2,160 



The test tubes were kept in the incubator at 21-24 C. 



It therefore appears that : 



(1) In unsterilised water the cholera bacilli quickly diminish, 

 whilst the water bacteria quickly multiply. 



(2) The addition of common salt at first has little or no 

 action on the cholera vibrios, but, with an increasing amount of 

 salt, the vibrios undergo considerable multiplication ; the water 

 bacteria multiply rapidly on the addition of the smallest amount 

 of salt. 



(3) After the addition of sodium sulphide the vibrios rapidly 

 disappear. 



(4) After the addition of sodium sulphide and sodium 

 chloride the cholera vibrios undergo rapid multiplication. 



When sodium chloride and sodium carbonate were added 

 to the unsterilised well-water, the water bacteria rapidly 

 multiplied, but the cholera vibrios could not be isolated after 

 the fourth day. When, however, sodium sulphide, in addition 

 to sodium chloride and sodium carbonate, was added to the 

 water, the cholera vibrios underwent considerable multiplication 

 and could be isolated up to the seventh day. At a lower- 

 temperature of 12*5 16 C. the addition of sodium chloride, 

 di-sodium phosphate, and sodium sulphide enabled the spirilla 

 to be isolated up to the ninth day. As a result of all his 

 experiments, Trenkmann states that the addition of sodium 

 chloride and sodium sulphide to a water causes a rapid disap- 

 pearance of many species of water bacteria, and very often 

 only a few species, sometimes only one, remain in conjunction 

 with the cholera vibrios. He also points out that water fouled 



