590 FRAGMENTS OF SCIENCE. 
and abroad have based upon it a triumphant demonstration 
of their doctrine. It is proved, they say, by the deport- 
ment of the mineral solution that neither bacteria nor 
their germs exist in the air; hence, if, on exposing a 
thoroughly sterilized turnip infusion to the air, bacteria 
appear, they must of necessity have been spontaneously 
generated. In the words of Dr. Bastian: " We can only 
infer that while the boiled saline solution is quite incapable 
of engendering bacteria, such organisms are able to arise 
de novo in tlie boiled organic infusion." * 
I would ask my eminent colleague what he thinks of 
this reasoning now? The datum is '' A mineral solution 
exposed to common air does not develop bacteria;" the 
inference is " Therefore if a turnip infusion similarly 
exposed develop bacteria, they must be spontaneously 
generated." The inference, on the face of it, is an 
unwarranted one. But while as matter of logic it is incon- 
clusive, as matter of fact it is chimerical. London air is 
as surely charged with the germs of bacteria as London 
chimneys are with smoke. The inference just referred to 
is completely disposed of by the simple question: " Why, 
when your sterilized organic infusion is exposed to optically 
pure air, should this generation of life de novo utterly 
cease? Why should I be able to preserve my turnip-juice 
side by side with your saline solution for the three hundred 
and sixty-five days of the year, in free connection with the 
general atmosphere, on the sole condition that the portion 
of that atmosphere in contact with the juice shall be 
visibly free from floating dust, while three days' exposure 
to that dust fills it with bacteria?" Am I over sanguine 
in hoping that as regards the argument here set forth he 
who runs may read, and he who reads may understand? 
We now proceed to the calm and thorough consideration 
of another subject, more important if possible than the 
foregoing one, but like it somewhat difficult to seize by 
reason of the very opulence of the phraseology, logical and 
rhetorical, in which it has been set forth. The subject 
now to be considered relates to what has been called " the 
death-point of bacteria." Those who happen to be 
acquainted with the modern English literature of the 
question will remember how challenge after challenge has 
*" Proceedings of the Royal Society," vol. xxi., p. 130. 
