104 LOUIS PASTEUK. 



of the clear infusion to reach the extremity of the 

 bent part of the neck where the dust particles are 

 arrested, and if this drop be then allowed to trickle 

 back into the infusion, the result is the same tur- 

 bidity supervenes and the microscopic organisms are 

 developed. Finally, if one of those bulbs which have 

 stood the test of months and years without alteration 

 be several times shaken violently, so that the external 

 air shall rush into it, and if it be then placed once 

 more in the stove, life will soon appear in it. 



In 1860 the Academy of Sciences had offered a 

 prize, the conditions of which were stated in the 

 following terms : 



' To endeavour by well-contrived experiments to 

 throw new light upon the question of spontaneous 

 generation.' The Academy added that it demanded 

 precise and rigorous experiments equally well studied 

 on all sides; such experiments, in short, as should 

 render it possible to deduce from them results free 

 from all confusion due to the experiments themselves. 

 Pasteur carried away the prize, and no one, it will be 

 acknowledged, deserved it better than he. Neverthe- 

 less, to his eyes, the subject was still beset with diffi- 

 culties. In the hot discussions to which the question 

 of spontaneous generation gave rise, the partisans of 

 the doctrine continually brought forward an objection 

 based on an opinion already referred to, and first 

 enunciated by Gay-Lussac. As already known to the 



