94 THE LIFE OF PASTEUR 



contained in the air ; the cotton wool often became black with 

 those various kinds of dust. Pasteur assured himself that 

 amongst various detritus those dusts presented spores and 

 germs. " There are therefore in the air some organized cor- 

 puscles. Are they germs capable of vegetable productions, or 

 of infusions? That is the question to solve." He undertook 

 a series of experiments to demonstrate that the most putrescible 

 liquid remained pure indefinitely if placed out of the reach of 

 atmospheric dusts. But it was sufficient to place in a pure 

 liquid a particle of the cotton-wool filter to obtain an immediate 

 alteration. 



A year before starting any discussion Pasteur wrote to 

 Pouchet that the results which he had attained were " not 

 founded on facts of a faultless exactitude. I think you are 

 wrong, not in believing in spontaneous generation (for it is 

 difficult in such a case not to have a preconceived idea) , but in 

 affirming the existence of spontaneous generation. In ex- 

 perimental science it is always a mistake not to doubt when 

 facts do not compel affirmation. ... In my opinion, the ques- 

 tion is whole and untouched by decisive proofs. What is there 

 in air which provokes organization? Are they germs? is it a 

 solid? is it a gas? is it a fluid? is it a principle such as ozone? 

 All this is unknown and invites experiment." 



After a year's study, Pasteur reached this conclusion : 

 "Gases, fluids, electricity, magnetism, ozone, things known 

 or things occult, there is nothing in the air that is conditional 

 to life, except the germs that it carries." 



Pouchet defended himself vigorously. To suppose that germs 

 came from air seemed to him impossible. How many millions 

 of loose eggs or spores would then be contained in a cubic 

 millimetre of atmospheric air? 



'What will be the outcome of this giant's struggle?" 

 grandiloquently wrote an editor of the Moniteur Scientifique 

 (April, 1860). Pouchet answered this anonymous writer by 

 advising him to accept the doctrine of spontaneous generation 

 adopted of old by so many " men of genius." Pouchet 's prin- 

 cipal disciple was a lover of science and of letters, M. Nicolas 

 Joly, an agrege of natural science, doctor of medicine, and pro- 

 fessor of physiology at Toulouse. He himself had a pupil, 

 Charles Musset, who was preparing a thesis for his doctor's 

 degree under the title : New Experimental Researches on 

 Heterogenia, or Spontaneous Generation. By the words 



