THE QUESTION OF SPONTANEOUS GENERATION. 101 



By an ingenious method he sowed the contents of 

 the cotton wool in the same liquids that had been 

 rendered sterile by boiling. The liquids became fertile, 

 even more fertile than if they had been exposed to the 

 free contact of atmospheric air. Now, what was there 

 in the dust contained in the cotton wool? Only 

 amorphous particles of silk, cotton, starch; and, 

 along with these, minute bodies which, by their trans- 

 parency and their structure, were not to be distin- 

 guished from the germs of microscopic organisms. 

 The presence of imponderable fluids could not here be 

 pleaded. 



Nevertheless, fearing that determined scepticism 

 might still attribute to the cotton wool an influence of 

 some sort on account of its being an organised sub- 

 stance, Pasteur substituted for the stoppers of cotton 

 wool stoppers of asbestos previously heated to red- 

 ness. The result was the same. 



Wishing still further to dispose of the hypothesis 

 that, in ordinary air, an unknown something existed 

 which, independent of germs, might be the cause 

 of the observed microscopic life, Pasteur began a new 

 series of experiments as simple as they were demon- 

 strative. Having placed a very putrescible infusion 

 in other words, one very appropriate to the appearance 

 of microscopic organisms in a glass bulb with a long 

 neck, by means of the blowpipe, he drew out this neck 



