DUST AND DISEASE. 33 



Insect life, moreover, is sometimes exhibited with 

 monstrous prodigality at Alpine heights. 



In a fifth series of experiments sixteen bottles were 

 filled with infusions. Into four of them, while cold, 

 ordinary unheated and unsifted air was pumped, and 

 in these fungi were developed. Into four other 

 bottles, containing a boiling infusion, ordinary air was 

 also pumped — no fungi were here developed. Into 

 four other bottles containing an infusion which had 

 been boiled and permitted to cool, sifted air was pumped 

 — no fungi were developed. Finally, into four bottles 

 containing a boiling infusion sifted air was pumped — 

 no fungi were developed. Only, therefore, in the four 

 cases where the infusions were cold infusions, and the 

 air ordinary air, did fungi appear. 



Dr. Bennett does not draw from his experiments the 

 conclusion to which they so obviously point. On the 

 contrary, he founds on them a defence of the doctrine of 

 spontaneous generation, and a general theory of sponta- 

 neous development. So strongly was he impressed with 

 the idea that the germs could not possibly pass through 

 his potash and sulphuric acid tubes, that the appear- 

 ance of fungi, even in a small minority of cases, where 

 the air had been sent through these tubes, was to him 

 conclusive evidence of the spontaneous origin of such 

 fungi. And he accounts for the absence of life in many 

 of his experiments by an explanation which will not 

 bear a moment's criticism. But knowing, as we now do, 

 that organic particles may pass unscathed through 

 alkalies and acids, the results of Dr. Bennett are pre- 

 cisely what ought under the circumstances to be ex- 

 pected. Indeed, their harmony with the conditions 

 now revealed is a proof of the honesty and accuracy 

 with which they were executed. 



The caution exercised by Pasteur both in the exe- 



*D 



