PATHOGENIC BACTERIA IN DIFFERENT WATERS 331 



In order to show that this attenuation of the tetanus 

 virus in unsterihsed waters is due to the presence of 

 other bacteria, Schwarz inoculated steriHsed sea-water, 

 not with a pure culture of tetanus, but, on the contrary, 

 with an impure though virulent cultivation. Instead 

 of the tetanus remaining for an indefinite length of 

 time in a virulent condition, as had previously been ob- 

 served in the case of sterilised sea-water, it was found 

 to have become on the twentieth day already so attenu- 

 ated, that on inoculating animals in the usual manner 

 with some of the water their death only took place 

 after a lapse of twenty-one days from the date of in- 

 oculation, and unaccompanied by any typical tetanic 

 symptoms excepting extreme emaciation. 



It will be seen from a careful study of the numerous 

 investigations which have been made on the behaviour 

 of pathogenic organisms in water what enormous dif- 

 ferences exist in their capacity for living in this me- 

 dium ; that whereas some varieties are destroyed in a 

 few hours, some will live and flourish for many months. 

 Moreover, it is obvious how greatly in some cases the 

 character of the water influences the vitality of the 

 micro-organisms, a point which is especially brought 

 out in Trenkmann's experiments on the cholera bacillus ; 

 and it is of particular interest to note how in the case 

 of unsterilised waters the ordinary water bacteria are 

 able to overwhelm and suppress those foreign patho- 

 genic forms which have been introduced. Kraus's ex- 

 periments are particularly instructive in this respect, 

 for they exhibit the multiplication which takes place 

 in the ordinary water bacteria, and the simultaneous 

 disappearance which ensues of the pathogenic or- 

 ganisms introduced. The experiments on anthrax 

 demonstrate conclusively the immensely greater vital 

 powers possessed by the spore over the bacillar form 



