330 MICRO-ORGANISMS IN WATER 



therefore, that the bacilli introduced directly from the 

 body of an animal are more vigorous and virulent than 

 those taken from cultures ; also that the simultaneous 

 introduction of culture material with the bacilli serves 

 to prolong the virulence of the latter. 



The experiments on the behaviour of the sporiferous 

 tetanus bacillus are amongst the most interesting which 

 have been made in connection with the vitality of patho- 

 genic bacteria in water. In some respects the results 

 resemble those obtained by one of us on anthrax spores 

 thus, in the practically indefinite virulence in sterile 

 waters, and the degeneration in unsterile ones. Alto- 

 gether unique, however, is the recrudescence of the 

 virulence exhibited by the tetanus bacilli, which is an 

 observation of such fundamental importance as to de- 

 mand further investigation. 



Schwarz explains this attenuation of the tetanus 

 organisms in the unsterilised waters as a consequence 

 of the multiplication of the ordinary water bacteria 

 present. He examined by means of plate culture the 

 behaviour of the latter, and found that from the day 

 of the introduction of the tetanus bacilli until the 

 period when the attenuation of the latter was observed 

 these water forms multiplied steadily, until the point 

 was reached to which we have so often referred when 

 their numbers again began to diminish. Schwarz 

 throws out the suggestion that the attenuation of the 

 tetanus organism may not only be due to the extensive 

 multiplication of the water bacteria, stimulated by the 

 culture-material which was introduced when the waters 

 were first infected with tetanus, but may also depend 

 upon the particular varieties of water microbes present ; 

 and that the recovery of their virulence by the former 

 may be due to the subordination of the latter when 

 their diminution became marked. 



