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air, that has produced the effects observed ? What is 

 this something ? A sunbeam entering through a chink 

 in the roof or wall, and traversing the air of the loft, 

 would show it to be laden with suspended dust particles. 

 Indeed the dust is distinctly visible in the diffused day- 

 light. Can it have been the origin of the observed life ? 

 If so, are we not bound by all antecedent experience to 

 regard these fruitful particles as the germs of the life 

 observed ? 



The name of Baron Liebig has been constantly 

 mixed up with these discussions. ' We have,' it is said, 

 ' his authority for assuming that dead decaying matter 

 can produce fermentation.' True, but with Liebig 

 fermentation was by no means synonymous with life. 

 It meant, according to him, the shaking asunder by 

 chemical disturbance of unstable molecules. Does the 

 life of our flasks, then, proceed from dead particles ? 

 If my co-enquirer should reply ' Yes,' then I would ask 

 him, * What warrant does Nature offer for such an 

 assumption? Where, amid the multitude of vital 

 phenomena in which her operations have been clearly 

 traced, is the slightest countenance given to the notion 

 that the sowing of dead particles can produce a living 

 crop?' With regard to Baron Liebig, had he studied 

 the revelations of the microscope in relation to these 

 questions, a mind so penetrating could never have 

 missed the significance of the facts revealed. He, how- 

 ever, neglected the microscope, and fell into error but 

 not into error so gross as that in support of which his 

 authority has been invoked. Were he now alive, he 

 would, I doubt not, repudiate the use often made of his 

 name Liebig's view of fermentation was at least a 

 scientific one, founded on profound conceptions of 

 molecular instability. But this view by no means 

 involves the notion that the planting of dead particles 



