252 BIOGENESIS AND ABIOGENESIS Till 



quarter of an hour ; and, while the steam is passing 

 out, stop the neck of one with a large plug of 

 cotton-woo!, so that this also may be thoroughly 

 steamed. Now set the flasks aside to cool, and, 

 when their contents are cold, add to one of the open 

 ones a drop of filtered infusion of hay which has 

 stood for twenty-four hours, and is consequently 

 full of the active and excessively minute organisms 

 known as Bacteria. In a couple of days of ordinary 

 warm weather the contents of this flask will be 

 milky from the enormous multiplication of Bacteria. 

 The other flask, open and exposed to the air, will, 

 sooner or later, become milky with Bacteria, and 

 patches of mould may appear in it ; while the liquid 

 in the flask, the neck of which is plugged with 

 cotton- wool, will remain clear for an indefinite 

 time. I have sought in vain for any explanation 

 of these facts, except the obvious one, that the air 

 contains germs competent to give rise to Bacteria, 

 such as those with which the first solution has 

 been knowingly and purposely inoculated, and to 

 the mould-^m^'. And I have not yet been able 

 to meet with any advocate of Abiogenesis who 

 seriously maintains that the atoms of sugar, tar- 

 trate of ammonia, yeast-ash, and water, under no in- 

 fluence but that of free access of air and the ordinary 

 temperature, re-arrange themselves and give rise 

 to the protoplasm of Bacterium. But the alterna- 

 tive is to admit that these Bacteria arise from 

 germs in the air ; and if they are thus propagated, 



