254 BIOGENESIS AND ABIOGENESIS vill 



conceive that they should not be suspended in the 

 atmosphere in myriads. 



Thus the evidence, direct and indirect, in favour 

 of Biogenesis for all known forms of life must, I 

 think, be admitted to be of great weight. 



On the other side, the sole assertions worthy 

 of attention are that hermetically sealed fluids, 

 which have been exposed to great and long-con- 

 tinued heat, have sometimes exhibited living 

 forms of low organisation when they have been 

 opened. 



The first reply that suggests itself is the prob- 

 ability that there must be some error about these 

 experiments, because they are performed on an 

 enormous scale every day with quite contrary 

 results. Meat, fruits, vegetables, the very ma- 

 terials of the most fermentable and putrescible 

 infusions, are preserved to the extent, I suppose I 

 may say, of thousands of tons every year, by a 

 method which is a mere application of Spallan- 

 zani's experiment. The matters to be preserved 

 are well boiled in a tin case provided with a small 

 hole, and this hole is soldered up when all the air 

 in the case has been replaced by steam. By this 

 method they may be kept for years without 

 putrefying, fermenting, or getting mouldy. Now 

 this is not because oxygen is excluded, inasmuch 

 as it is now proved that free oxygen is not neces- 

 sary for either fermentation or putrefaction. It 

 is not because the tins are exhausted of air, for 



