590 FRAGMENTS OF 



and abroad have based upon it a triurn pliant 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 the 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 rims 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 tlie Royal Society," vol. xxi., p. 130. 



