546 FRAGMENTS OF SCIENCE. 
years, the beef-tea within the chamber is found in 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 abso- 
lutely no difference between the air within and that with- 
out save that the one is dustless and the other dust-laden. 
Clinch the experiment thus: Open the door of your cham- 
ber and allow the dust to enter it. In three days after- 
ward 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 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 " Philoso- 
phical Transactions/' it would be simply monstrous to 
affirm that these swarming crops of bacteria are sponta- 
neously 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 the 
common practices of life. Heat kills the bacteria, cold 
numbs them. When my housekeeper has pheasants in 
charge which she wishes to keep sweet, but which threaten 
to give way, she partially cooks the birds, kills the infant 
