FUNGI. 311 



end of it, he placed an aspirator, a contrivance for 

 causing a current of the external air to pass through 

 the tube. He kept this apparatus going for four and 

 twenty hours, and then removed the dusted gun- 

 cotton, and dissolved it in alcohol and ether. He 

 then allowed this to stand for a few hours, and the 

 result was, that a very fine dust was gradually 

 deposited at the bottom of it. That dust, on being 

 transferred to the stage of a microscope, was found to 

 contain an enormous number of starch grains. We 

 know that the materials of our food, and the greater 

 portions of plants are composed of starch, and we are 

 constantly making use of it in a variety of ways, so 

 that there is always a quantity of it suspended in the 

 air. It is these starch grains which form many of 

 those bright specks that we see dancing in a ray of 

 light sometimes. But, besides these, M. Pasteur 

 found also an immense number of other organic 

 substances, such as spores of fungi, which had been 

 floating about in the air, and had got caged in this 

 way. 



" He went farther, and said to himself, * If these 

 really are the things that gave rise to the appear- 

 ance of spontaneous generation, I ought to be able to 

 take a ball of this dusted gun-cotton, and put it into 

 one of my vessels containing that boiled infusion, 

 which has been kept away from the air, and in which 

 no infusoria are at present developed, and then, if I 

 am right, the introduction of this gun-cotton will give 

 rise to organisms.' Accordingly, he took one of 

 these vessels of infusion, which had been kept 

 eighteen months, without the least appearance of 



