Appendix. 165 



form and the air is very still. The number containing organisms 

 was very much less than in those filled in the garden of the same 

 building. Pasteur predicted that if flasks could be opened and 

 closed in deep cellars with absolutely no disturbance caused by 

 the entrance of the operator there would be the same absence of 

 vitality as in flasks which had been long exposed to red heat.* 

 Later on he learned, what he had also predicted, that by simply 

 turning the long neck of his flasksf downward they might be kept 

 indefinitely without sealing or stoppers of cotton, and still no 

 organisms would show themselves, for by this simple expedient 

 the germs could not enter the flasks, gravity opposing. 



On the other hand, Pouchet, assisted by MM. Joly and 

 Musset, shortly afterward went over the same ground. He col- 

 lected the solid particles from the air by means of an instru- 

 ment which he called an aeroscope. This was a simple tube 

 drawn out to a point. Air was passed in a jet through this and 

 made to impinge upon a glass plate covered with some viscous 

 substance. A pile of dust was thus caught, and then submitted 

 to examination by the microscope. But strangely enough although 

 he found plenty of foreign materials, like coal-dust, starch-gran- 

 ules, etc., not a trace of organic life, either in shape of spores or 

 of germs. He was untiring in his researches. "He has," says 

 M. Joly, " examined the dust which finds its way into the respir- 

 atory cavities in man and the lower animals; that which has 

 been the accumulation of centuries in our Gothic cathedrals, 

 and that which floats in the air of our public halls, our theatres, 

 and our hospitals. He has crossed seas, climbed high moun- 



* In an unexpected direction Prof. Tyndall by his recent experiments 

 with closed boxes has practically verified this prediction, though the experi- 

 ments were not made with cellar air. The similarity of the two cases, how- 

 ever, is apparent. Vide postca, p. 175. 



t Many of Pasteur's flasks are still preserved in Paris, and by repeated 

 examination have been found to remain unchanged. As late as November, 

 1874, M. Balard, in presenting to the Academy of Sciences a paper by M. Ser- 

 vel, detailing experiments which the writer held to be demonstrative of spon- 

 taneous generation, took occasion to say that he had just then examined in 

 Pasteur's laboratory some of his unsealed flasks which contained blood that 

 had been drawn more than eleven years previously, and in which, during all 

 this time, no bacteria had appeared and no putrefaction had taken place. 



