POUCHET, PASTEUR: THE GERMS OF THE AIR 91 



when he introduces air which he has simply made to 

 bubble through concentrated sulphuric acid. One of 

 these experiments lasted from May to August, but, al- 

 though this air was incessantly renewed, it never caused 

 any production of Infusoria: this proved that Gay- 

 Lussac was wrong, and Spallanzani right. 



The following year Schwann obtained the same result 

 as Schultze by using air heated by passage through a 

 bath of fusible alloy. Later (1854), Schroeder and 

 Dusch replaced the heated air by air simply filtered 

 through cotton, and from them dates the introduction 

 into microbiology of cotton plugs for filtering air. 



Reading to-day of their experiments, we ask ourselves 

 why they did not bring universal conviction. What 

 did they signify save this: that there was in the air a 

 principle of life which sulphuric acid, heat filtration, 

 through cotton, destroyed? This principle was, there- 

 fore, neither a gas nor a vapor, nor one of those solid 

 bodies which heat respects. It could only be an organic 

 substance. How is it that Schwann and Schultze did 

 not as resolutely bring the partisans of spontaneous 

 generation face to face with this dilemma, as Pasteur was 

 to do 10 years later: this organic substance which heat 

 and sulphuric acid destroy, which cotton arrests, can 

 only be living or dead. Why, being forced to choose, do 

 you take the hypothesis the most contradictory to that 

 offered by the best known branches of science? 



Ill 

 POUCHET, PASTEUR: THE GERMS OF THE AIR 



In order to assume this tone of authority, it would 

 have been necessary to confront the partisans of spon- 

 taneous generation with some experiments which were 



