62 ORIGINATION OF LIVING BEINGS 



he managed to break it open and introduce such a ball of 

 Kim-cotton, without allowing the infusion or the cotton 

 hall to come into contact with any air but that which had 

 n subjected to a red heat, and in twenty-four hours he 

 had the satisfaction of finding all the indications of what 

 had been hitherto called spontaneous generation. He had 

 succeeded in catching the germs and developing organisms 

 in the way he had anticipated. 



It now struck him that the truth of his conclusions 

 might be demonstrated without all the apparatus he had 

 employed. To do this, he took some decaying animal or 

 vegetable substance, such as urine, which is an extremely 

 decomposable substance, or the juice of yeast, or perhaps 

 some other artificial preparation, and filled a vessel having 

 a long tubular neck, with it. He then boiled the liquid 

 and bent that long neck 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 

 \vhich were constantly floating in the air. 



To this conclusion, however, the objection was made, 

 th:it 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 exaggerated view has been held on that sub- 

 j( ( t ; he showed that the chances of animal or vegetable 

 life appearing in infusions, depend entirely on the con- 

 ditions 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 from a great height, or from 

 some very quiet cellar, you will often not find a single trace 

 of life. 



