100 PASTEUR: THE HISTORY OF A MIND 



becomes populated just as if the neck had been broken 

 off. Another proof is this: when the neck is removed 

 one often sees (Fig. 12) the first development of growth 

 directly under the opening, where the germs from the air 

 have fallen in." 



RESPONSE TO THE ARGUMENTS IN FAVOR OF 

 SPONTANEOUS GENERATIONS 



"I am not content," Pasteur might have continued, 

 condensing his powerful argument, "I am not content 

 with giving you convincing experiments which always 

 succeed. I do more than that. I explain why my 

 predecessors have so often obtained those contradictory 

 results which have troubled them and stayed their 

 decisions. Thus, always, Schwann and the others have 

 seen their best-contrived experiments fail when they 

 placed their liquids, if only for an instant, in contact 

 with mercury. What imprudence! Is not the mercury 

 constantly and necessarily full of impurities? Those 

 particles of dust which come to it from the air, and 

 which collect on its surface, mingle with it and are 

 carried along with it everywhere. It is for this reason 

 that I have carefully excluded it from all the preceding 

 experiments, which, performed with its aid, might have 

 been easier to carry out, but which might have left us 

 uncertain as to the results. 



"And then, to disturb our convictions, there is also the 

 history of this milk which curdles or putrefies under 

 conditions where beef bouillon, the must of beer, and 

 other infusions remain unaltered. There is this yolk of 

 egg, or this meat without water, which we cannot pre- 

 serve by heating to 100 C. and keeping afterwards in 



