FOREWORD 17 



as the results of the experiments recorded would 

 still probably be held to be absolutely at variance 

 with the everyday procedures of bacteriologists. 

 A distinguished physiologist indeed recently sug- 

 gested to me as an a priori objection to my results 

 that, if true, " the whole of modern bacteriology, 

 with its isolation of different forms of bacteria in 

 pure cultivation, must go by the board, since no 

 method of sterilisation could be held to prevent 

 the development of micro-organisms spontaneously 

 differing from those which had been placed in any 

 given cultivating medium by inoculation." 



But this is a mistake, as I have elsewhere pointed 

 out. The different results in the two cases are 

 entirely due to difference of aim and procedure. 

 The bacteriologist wishes to make doubly sure that 

 the media he uses will no longer contain living 

 micro-organisms or their germs. Therefore he 

 superheats them to a degree sufficient to destroy 

 what I may call the " germinality ' of the fluids, 

 while leaving such fluids still capable of nourish- 

 ing the organisms introduced by inoculation. He 

 heats them, therefore, two or three times to 100 

 C. or else once to 130 C., that is to a temperature 

 far higher than would be needed to kill any organ- 

 isms that could possibly be found in his tubes, and 



