242 HOW LIFE BEGAN 



Many scientists were now willing to accept the fact that living 

 organisms did not originate spontaneously. 



The revival of the discussion. After some years of practically 

 no discussion on the subject, Pouchet, in 1859, suddenly revived the 

 controversy. He believed that spontaneous generation was one 

 of the means employed by nature for the production of living 

 things, so he set out to prove it. He filled a bottle with boiling 

 water and inverted it with the mouth of the bottle under mercury. 

 Then, by means of a deliver}^ tube, he introduced oxygen through 

 the mercury into the bottle of water. The oxygen gradually dis- 

 placed some of the water. By means of a pair of forceps, which 

 he had first heated, he thrust some hay through the mercury into 

 the bottle. The hay, too, had been carefully heated to a very high 

 temperature. The hay floated in the water in the bottle, in the 

 oxygen atmosphere. IMicroorganisms appeared in great numbers. 



Louis Pasteur enters the controversy. A French scientist, 

 Louis Pasteur, thought that Pouchet had not set up his experiment 

 carefully enough and that germs must have entered with the oxygen 

 or hay. Pouchet asked how it was possible for air to contain so 

 many germs that they developed in every organic material. He 

 said the air would be misty with them. Pasteur began to wonder 

 whether germs might not be more numerous in some air than in 

 other air. 



In order to investigate this, Pasteur filled a number of glass 

 flasks with a liquid that would easily spoil. He boiled the liquid 

 and sealed the flasks while the liquid was still boiling. He opened 

 some of the bottles in different places where there were people 

 and dust. He then sealed the flasks again, and in all cases organ- 

 isms appeared. He next w^ent to the Alps to investigate air at an 

 altitude so high that it would be free from dust. He went to the 

 Mer de Glace, high up in the Alps. He opened twenty of the 

 flasks that had been carefully prepared, and immediately sealed 

 them again. Subsequently, microorganisms appeared in only one 



