PATHOGENIC BACTERIA IN DIFFERENT WATERS 331 



, In order to show that this attenuation of the tetanus 

 virus in unsterilised waters is due to the presence of 

 other bacteria, Schwarz inoculated sterilised 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 



