Report on the Bacteriology of Water. 



241 



for after 56 hours' insolation the number of anthrax spores was 

 greatly diminished, and after 84 hours' exposure to solar radiation 

 the presence of anthrax was no longer demonstrable by cultivation 

 at all (pp. 209—213). 



As regards the virulence of the anthrax in the sterilised waters of the 

 Thames and Loch Katrine, the experiments which I have performed on 

 mice conclusively prove that this is maintained over long periods of 

 ti mtJ — many months. In no single instance did the injection of 1 c.c. 

 of these waters fail to kill the mouse, although the anthrax spores 

 had been in the Thames water for upwards of seven months, and for 

 upwards of three months in that of Loch Katrine. There is, however, 

 unmistakable evidence of the rapidity of the lethal action of the 

 anthrax depending on the number of spores present in the water. 

 Thus in the First Series of Thames water experiments, in which only 

 a small number of anthrax spores were present, the porcelain-filtered 

 water was fatal in 4 days 17 hours, the steam-sterilised water which 

 had been exposed to daylight was also fatal in 4 days 17 hours, and 

 the porcelain-filtered water similarly exposed to daylight killed the 

 mouse in 6 days 20| hours ; on the other hand, in the Second Series of 

 Thames water experiments, in which a much larger number of 

 anthrax spores were present in the water, the porcelain-filtered was 

 fatal in 2 days 5 hours, and the steam-sterilised in 2 days 21 hours ; 

 and again in the case of the Loch Katrine water, in which a still 

 larger number of anthrax spores were present at the time of the ex- 

 periment, the porcelain-filtered killed in 2 days 17 hours, and the 

 steam-sterilised in 1 day 20 hours (pp. 204—206, 224, 225, 239). 



Of the sterilised Thames waters exposed to direct sunshine, neither 

 the porcelain-filtered nor the steam-sterilised was fatal to mice, nor 

 could their virulence be revived by the addition of broth to the 

 water (pp. 209, 212). 



4. In the unsterilised Thames water, both of the First and Second 

 Series of experiments, the anthrax spores were indeed found to be 

 still present in a vital state after many months, but in greatly 

 diminished numbers, and thus furnishing the most striking contrast 

 to their behaviour in the same water when sterilised either by steam 

 or by porcelain filtration. 



In the unsterilised Thames water of the First Series of experi- 

 ments, anthrax was only just discoverable by the special method of 

 cultivation which I devised for the purpose (see p. 185) 4 months 

 after infection, so that it must have undergone great diminution in 

 numbers during this period (pp. 195, 196, 198, 199). 



This diminution in the number of anthrax spores was further 

 established by the experiments on animals. Thus, when mice were 

 subcutaneously injected with 1 c.c. of these unsterilised waters of the 

 First Series, 7 months after the anthrax spores had been introduced, 



