Report on the Bacteriology of Water. 



209 



6. Vitality and Virulence of Anthrax in Thames Water (First Series) 

 Exposed to Direct Sunshine. 



The effect of direct sunshine is recorded in Table VII. The flasks 

 were taken from the incubator and refrigerator respectively on 

 March 25, 1892; they remained in a dark room from that day to 

 April 9, 1892, and from then onwards they were exposed to as much 

 sunshine as could be conveniently obtained, and which was approxi- 

 mately estimated in hours, although it is obviously very difficult to 

 make any exact determination of the latter. The conditions of 

 experiment are, of course, also much complicated by the fact that the 

 temperature of the water so exposed was subject to very great varia- 

 tion, although it certainly never exceeded 32° C. 



The results, which are very striking, are easily followed by reference 

 to Table VII. 



From the table it will be seen that in — ■ 



JJnfiltered Thames water, anthrax was still alive on May 2, 1892, 

 after 56 hours' sunshine, but extinct on May 12, 1892, after about 

 84 hours' insolation. 



Taper-filtered Thames water, anthrax was almost extinct on May 15, 

 1892, after about 92 hours' insolation, and quite extinct on June 17, 

 1892, after about 151 hours' sunshine. 



Thames water filtered through porcelain, anthrax was still alive on 

 May 2, 1892, after about 56 hours of sun, but extinct on May 12, 

 1892, after about 84 hours' insolation. 



Thames water sterilised with steam, anthrax was still alive on 

 May 2, 1892, after about 56 hours', but dead on May 12, 1892, after 

 about 84 hours' sunshine. 



In consequence of the sunshine having destroyed the greater num- 

 ber of those water bacteria causing liquefaction of the gelatine, it 

 was possible to incubate the plates for a long period of time, and 

 thus in most instances to dispense with the special method of 

 examination by preliminary heating already so often referred to. 



The above results have only reference to the presence or absence of 

 anthrax as revealed by cultivation, but experiments were also made 

 on the virulence of these waters which had been exposed to direct 

 insolation. Thus : — 



Animal Experiment No. 30. — On November 2, 1892, 1 c.c. of the 

 water from the flask " 4 I, Thames water, unfiltered, and infected 

 with anthrax on March 18, 1892, exposed to 151 hours' sunshine," 

 was subcutaneously injected into a white mouse. The mouse is still 

 alive (November 14, 1892). 



Animal Experiment No. 31. — On November 2, 1892, 1 c.c. of the 

 water from flask " 4 I, Thames water steam -sterilised, and infected 

 with anthrax on March 18, 1892, exposed to 151 hours' sunshine," 



