Report on the Bacteriology of Water. 



273 



aquatic forms developing so rapidly, and some of them so quickly liquefy- 

 ing the gelatine, that even when plenty of anthrax exists on the plates 

 the latter are rendered useless before they can be got to develop visible 

 colonies. 



On comparing Tables C (III) and C (IV) the result comes out 

 that both weak and strong anthrax can hold their own for some time 

 in the filtered Thames water, and that this is not a mere case of their 

 lying passive and unchanged in it ; indeed, without laying undue 

 stress on the actual numbers, the general result seems to be that this 

 schizomycete multiplies vegetatively under the conditions given, and 

 then passes over into spores. I say this seems to be the case; but it 

 is much more likely that the apparent increase at first is due to the 

 breaking up of the bacilli into shorter rodlets, most of which die at last. 



That spores were really present we proved, as before, by sub- 

 mitting samples of each of the waters to 60° C. for 24 hours, and 

 then cultivating plates from them ; the beautifully pure cultures of 

 anthrax obtained showed clearly that spores had been formed. 



I are aware of the criticism that the vegetative growth exhibited 

 by both the weak and strong anthrax was probably not entirely 

 at the expense of the organic materials already in the filtered water, 

 but was no doubt in part due to small quantities of food materials 

 introduced with the infecting material (and possibly in part also due 

 to substances derived from decomposing bacteria) ; but the reply is 

 (1) that the quantity of food materials introduced by our mode of 

 infection was very small, and (2) that it does not affect the practical 

 question much, because in nature such minimum fouling of the water 

 would be likely to occur when anthrax finds its way to the river. 

 Of course the criticism should be borne in mind, however, and our 

 experimental results do not support the idea that anthrax can 

 multiply vegetatively in waters containing only minimum traces of 

 food materials. 



If we compare Tables c (V) and c (VI) the fact again appears to 

 come out that the anthrax bacillus, whether strong or weak as regards 

 its virulence, behaves very like an ordinary water form when first 

 placed in Thames water sterilised by steam. Here, again, the ex- 

 planation given above no doubt applies. Moreover, it is again 

 evident that, as time goes on, the plates need more incubating to 

 bring out the bacilli, and the numbers are then very large — cf. the 

 events of the third day — a fact which again raised our suspicions as 

 to the development of spores. As before, moreover, we tested this 

 suspicion by heating a sample of each water to 60° C. for twenty-four 

 hours, and obtained pure cultures of anthrax therefrom. 



