FERMENTATION. 255 



laden. Clinch the experiment thus : Open the door of 

 yonr chamber and allow the dust to enter it. In three 

 days afterwards you have every vessel within the chamber 

 swarming with bacteria, and in a state of active putre- 

 faction. Here, also, the inference is quite as certain 

 as in the case of the powder sown in your garden. 

 Multiply your proofs by building fifty chambers instead 

 of one, and by employing every imaginable infusion of 

 wild animals and tame ; of flesh, fish, fowl, and viscera ; 

 of vegetables of the most various kinds. If in all these 

 cases you find the dust infallibly producing its crop of 

 bacteria, while neither the dustless air nor the nutritive 

 infusion, nor both together, are ever able to produce 

 this crop, your conclusion is simply irresistible that the 

 dust of the air contains the germs of the crop which 

 has appeared in your infusions. I repeat there is no 

 inference of experimental science more certain than 

 this one. In the presence of such facts, to use the 

 words of a paper lately published in the ' Philosophical 

 Transactions,' it would be simply monstrous to affirm 

 that these swarming crops of bacteria are spontaneously 

 generated. 



Is there then no experimental proof of spontaneous 

 generation ? I answer without hesitation, none ! But 

 to doubt the experimental proof of a fact, and to deny 

 its possibility, are two different things, though some 

 writers confuse matters by making them synonymous. 

 In fact, this doctrine of spontaneous generation, in one 

 form or another, falls in with the theoretic beliefs of 

 some of the foremost workers of this age ; but it is 

 exactly these men who have the penetration to see, and 

 the honesty to expose, the weakness of the evidence 

 adduced in its support. 



And here observe how these discoveries tally with 



