92 PASTEUR: THE HISTORY OF A MIND 



irreproachable and always successful, l)ut no such were 

 available. Experiments which had been the most con- 

 vincing often failed, \Aithout any one being able to tell 

 why. Even to-day, when our technic is better, we can 

 not be sure of obtaining the results of Spallanzani. 

 Tyndall, whose experimental skill was very great, has 

 often repeated in vain the experiments of Schultze. In 

 short, there were certain substances, milk, albumen, 

 macerations of meat, which neither filtration, nor heating 

 of the air preserved from alteration, and we have seen 

 that Helmholtz admitted for these substances a kind of 

 spontaneous generation. But to admit it in one case, 

 was to admit it in all. Wherever there was a doubtful 

 case, one flask remaining fertile in spite of the precau- 

 tions taken, spontaneous generation had the right to 

 seize upon this result, and to say '*It is I who have pro- 

 duced this. Life is a fragile thing to preserve; more 

 fragile still to produce. It is all to no purpose that you 

 train your fingers to manipulate it delicately; you thwart 

 it without knowing it, and it is sometimes just because 

 you are unskilful that j^ou see it appear." 



And these were not the only reasons. The partisans 

 of spontaneous generation had the best of it in the dis- 

 cussion, and they could say: "We who do not know on 

 what life depends and who make it arise from nothing, 

 we are exempt from the obligation of showing you its 

 origin and causes. But you who attribute it to pre- 

 existing germs, show us then these germs! Above all, 

 show them to us in sufficient number and variety so 

 that each bubble of air can people with numerous and 

 varied organisms the various infusions which we may 

 ask it to fecundate. For, finally, specificity is one of the 

 consequences of your way of looking at things. But we 

 have not forgotten a certain experiment of Gay-Lussac 

 in which some grape juice, sterile at first, was made to 



