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but provided with tubes, through which air could 

 be made to reach the interior, and, as the essential 

 part of the experiment, the air thus made to enter 

 was transmitted either through sulphuric acid or a 

 heated tube for the purpose of killing anything of 

 a living nature that might happen to be present. 

 Thus circumstanced, and under the frequent re- 

 newal of air in contact with its surface, the liquid 

 remained for any length of time free from living 

 organisms, but when the mouth of the flask was 

 unclosed and its contents were freely exposed to 

 the air they were soon found to be swarming with 

 living beings. The natural conclusion to be drawn 

 from such an experiment is that it goes far towards 

 absolutely establishing that the air contains the 

 germs of living organisms and that it is these that 

 constitute the source of the microscopic organisms 

 found to become developed in the presence of 

 organic matter, which some have contended take 

 rise spontaneously. This view is supported by the 

 researches of the present day and nothing that 

 would bear the scrutiny of strict investigation has 

 ever been adduced against it. It stands at the 



