246 MICRO-ORGANISMS IN WATER 



remarks that the water acquires a taste immediately 

 after the introduction of this quantity of H^O^ ; but that 

 if the mixture is allowed to stand for 24 hours it is not 

 perceptible, and that this addition is perfectly harmless 

 from a dietetic point of view.) The samples examined 

 were tap-water containing 160 microbes per c.c, and 

 two samples of river-water containing, respectively, 600 

 and 6,000 organisms per c.c. 



After 7 days these various samples exhibited 3 

 organisms (tap-water), 2 (river- water with 600 per c.c), 

 and 10 organisms per c.c. (river-water containing 6,000 

 per c.c). Sterile tap-water (100 c.c.) was inoculated 

 with -| c.c. of drain-water, and then treated with a 

 similar proportion of peroxide of h3^drogen, and on the 

 6 th day no organisms whatever were found. 



Experiments were also made with the typhoid bacil- 

 lus. For this purpose 2 c.c. of a broth culture were 

 introduced into 98 c.c of unsterile tap-water, and per- 

 oxide of hydrogen added in the proportion of 1 : 1,000. 

 After 6 days an examination revealed no typhoid baciUi. 

 Similar results were obtained when 100 c.c. of sterile 

 tap-water, to which ^ c.c of sterile broth was added, 

 was inoculated with two drops of a recent typhoid broth- 

 culture. 



Cholera bacilli inoculated into sterile and unsterile 

 tap-water, respectively, also succumbed after 24 hours' 

 contact with this material when present in the propor- 

 tion of 1 : 1,000. 



According to Altehoefer, therefore, in order to ob- 

 tain sterile water by means of peroxide of hydrogen 

 it is necessary to use this material in larger quantities 

 than recommended by Tromp, the proportion recom- 

 mended as advisable being 1 : 1,000 parts of the water. 

 The solution of peroxide of hydrogen employed by 

 Altehoefer contained 9*70 per cent, of this material, and 



