ON DUST AND DISEASE. 163 



Bennett made a fourth series of experiments, in which, 

 previous to forcing in the air, he permitted the flasks 

 to cool. Into four bottles thus treated he forced pre- 

 pared air, and after a time found fungi in all of them. 

 What is his conclusion ? Not that the boiling hot 

 liquid, employed in his first experiments, had destroyed 

 such germs as had run the gauntlet of his apparatus ; 

 but that air which, previous to being sealed up, had 

 been exposed to a temperature of 212, is too rare to 

 support life. This conclusion is so remarkable that it 

 ought to be stated in Dr. Bennett's own words. ' It 

 may be easily conceived that air subjected to a boiling 

 temperature is so expanded as scarcely to merit the 

 name of air, and that it is more or less unfit for the pur^ 

 pose of sustaining animal or vegetable life.' 



Now numerical data are attainable here, and as a 

 matter of fact I live and flourish for a considerable 

 portion of each year in a medium of less density than 

 that which Dr. Bennett describes as scarcely meriting 

 the name of air. The inhabitants of the higher Alpine 

 chalets, with their flocks and herds, and the grasses 

 which support these, do the same; while the chamois 

 rears its kids in air rarer still. 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. In 

 these four bottles 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 



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