FERMENTATION. 269 



every case as sweet and clear, and as free from bacteria, 

 as it was at the moment when it was first put in. There 

 is absolutely no difference between the air within and 

 that without save that the one is dustless, and the other 

 dust-laden. Clinch the experiment thus: Open the door 

 of your 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 putrefaction. 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 cham- 

 bers 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 pro- 

 ducing 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 bac- 

 teria 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 ex- 

 actly these men who have the penetration to see, and 



