80 ORIGINATION OF LIVING BEINGS. 



into an S shape or zig-zag, leaving it open at the end. 

 The infusion then gave no trace of any appearance 

 of spontaneous generation, however long it might be 

 left, as all the germs in the air were deposited in the 

 beginning of the bent neck. He then cut the tube 

 close to the vessel, and allowed the ordinary air to 

 have free and direct access ; and the result of that 

 was the appearance of organisms in it, as soon as the 

 infusion had been allowed to stand long enough to 

 allow of the growth of those it received from the 

 air, which was about forty-eight hours. The result 

 of M. Pasteur's experiments proved, therefore, in the 

 most conclusive manner, that all the appearances of 

 spontaneous generation arose from nothing more than 

 the deposition of the germs of organisms which were 

 constantly floating in the air. 



To this conclusion, however, the objection was 

 made, that if that were the cause, then the air 

 would contain such an enormous number of these 

 germs, that it would be a continual fog. But M. 

 Pasteur replied that they are not there in anything 

 like the number we might suppose, and that an exag- 

 gerated view has been held on that subject; he showed 

 that the chances of animal or vegetable life appearing 

 in infusions, depend entirely on the conditions under 

 which they are exposed. If they are exposed to the 

 ordinary atmosphere around us, why, of course, you 

 may have organisms appearing early. But, on the 

 other hand, if they are exposed to air at a great 

 height, or in some very quiet cellar, you will ofteu not 

 find a single trace of life. 



