264 



Profs. Percy Frankland and Marshall Ward. 



does the behaviour of strong virulent anthrax, known to be capable 

 of producing vigorous spores, differ from that of weak or " attenu- 

 ated " anthrax, known to be less deadly to animals, though still 

 capable of forming spores if the right conditions are offered, in any 

 respects, and in any or all of the waters ? 



The virulent anthrax employed was obtained from Edinburgh (and 

 recorded as Cow No. 3), and was proved to be fatal to rabbits in 

 two days) ; the attenuated anthrax also came from Edinburgh (Cow 

 No. 1), and took five days to kill a rabbit. 



The experiments detailed in the following tables, C (I) to C (VI), 

 were arranged as follows : — 



I. Four flasks, two of a litre capacity, and two of half a litre each, 

 were filled with the crude Thames water, brought fresh from the river, 

 and infected forthwith with anthrax : one pair of flasks receiving 

 strong anthrax, the other weak anthrax : plate cultures were made 

 at once, and on each succeeding day, the flasks standing in an 

 incubator at 20 — 22° C, the whole time. 



II. Four similar flasks were filled with the Thames water, same 

 collection, filtered forthwith through porcelain (Chamberland filter), 

 and proved to be free from aquatic bacteria, and duplicate pairs 

 treated in exactly the same way. 



III. Four similar flasks were filled with the Thames water, same 

 collection, and treated exactly as before, excepting that the water was 

 sterilised by heating in a steam steriliser to 100° C. for two hours. 



IV. Finally, four similar flasks were filled with the raw Thames 

 water, exactly as in set I, excepting that no anthrax was added, as 

 we wished to determine by daily plate culture how the water 

 organisms of the normal water behaved apart from the anthrax. 



As regards the incubation and future care, &c, all the 16 flasks 

 were treated alike, and the conditions of comparison are, therefore, 

 the same. 



The infecting fluid was obtained as follows in each case : — Clean 

 sowings were taken from an active agar culture, then shaken up with 

 sterile distilled water, and some of the dilute sowing spread on 

 potato (in tubes) and incubated for 24 hours at 30° C. 



This gave vigorous vegetative cultures, free from spores, as we 

 satisfied ourselves by placing samples at 60° C. for 18 hours, and 

 then making plate cultures, and we then proceeded as follows : — 



The potato cultures were broken down in sterile distilled water, 

 care being taken to introduce as little potato as possible, and 

 charges of this placed in the flasks. Of each pair of flasks infected, 

 one received four times as much as the other ; the charge is re- 

 ferred to in the tables as " large," or " small," accordingly. It may 

 here be stated that in those cases where experience showed us that 

 large numbers of colonies were to be expected on the plates, we used 



