DISTRIBUTION OF GERMS IN THE AIR 103 



might have been deposited there. Furthermore, through- 

 out the operation he kept the flasks as high as possible 

 above his head, so as to avoid the dust from his clothing. 

 When the necks were broken, there was a hissing sound : 

 this was the air entering. The flasks were then re- 

 sealed in the flame of a lamp, and carried back to the 

 thermostat. 



In some cases, the air which entered contained viable 

 germs, and the infusion became populated with various 

 organisms; in others, the air contained nothing, and the 

 infusion remained sterile. There were always some flasks 

 which remained intact, although each had received from 

 200 to 300 cc. of external air. To say that there are 

 germs in the air is not, therefore, to say that they occur 

 everywhere, or even that they are very numerous : it is 

 saying that there are some here and none there, that we 

 find more in a low and humid place, favorable to crypto- 

 gamic vegetation; that we find fewer in air which is in 

 repose, like that of the cellar of the observatory; that they 

 will be the more rare the farther we go from cultivated 

 land, and the higher we ascend a mountain; that there 

 will be almost none in the midst of the Swiss glaciers 

 where no vegetation can live. Pasteur opened a great 

 number of flasks in the air of these various places, and 

 he always found that some of them remained sterile, and 

 and the greater the known purity of the air at the point 

 studied, the greater the number of these. 



All the researches made since have confirmed the truth 

 of this conclusion. The air is much less populated with 

 germs than has been supposed, much less, even, than 

 Pasteur thought. To-day men carry on with security, 

 in this regard, either in the laboratories or in surgical 

 wards, operations which they would not have dared to 

 undertake in 1862, haunted as they were by the idea of 

 those germs in the air, to which Pasteur had just called 



