116 VITALISM AND SCHOLASTICISM 



which we look at in a shop window is a stand- 

 ing proof of the truth of the facts which Pasteur 

 proclaimed. As to the other two experiments, 

 in the one case the bacteria are filtered out 

 of the air mechanically by the wad of cotton- 

 wool. The other is also a case of mechanical 

 separation, for the tubular neck of the vessel 

 being narrow and the bends in it frequent the 

 bacteria become deposited on the sides of the 

 tube before reaching the fluid contained within 

 the flask. As a result of these experiments 

 the view that all living matter is derived from 

 living matter is now almost universally held, 

 though, of course, what Pasteur really proved 

 was, not that living matter never arises from 

 non-living matter, but that by observing cer- 

 tain laws and taking the necessary precautions 

 certain substances which would otherwise be- 

 come invaded by Irving' things which would 

 seize upon them for their food, would be kept 

 intact from them. But as it was the appear- 

 ance, apparently spontaneously, of life in such 

 substances which had formed the foundation 

 of the theory of spontaneous generation it has 

 often, though inaccurately, been assumed that 

 Pasteur proved that spontaneous generation 

 does not take place. 



Since his time scientific opinion is unanimous 

 that there is no proof that spontaneous genera- 



