SPONTANEOUS GENERATION. 581 



inherent life, and placed in contact with air cleansed of its 

 visibly suspended matter, has any power to generate life 

 anew. 



Remembering then the number and variety of the infu- 

 sions employed, and the strictness of our adherence to the 

 rules of preparation laid down by the heterogenists them- 

 selves; remembering that we have operated upon the very 

 substances recommended by them as capable of furnishing, 

 even in untrained hands, easy and decisive proofs of spon- 

 taneous generation, and that we have added to their sub- 

 stances many others of our own if this pretended gener- 

 ative power were a reality, surely it must have manifested 

 itself somewhere. Speaking roundly, I should say that in 

 such closed chambers at least five hundred chances have 

 been given to it, but it has nowhere appeared. 



The argument is now to be clenched by an experiment 

 which will remove every residue of doubt as to the ability 

 of the infusions here employed to sustain life. We open 

 the back doors of our sealed chambers, and permit the 

 common air with its floating particles to have access to our 

 tubes. For three months they have remained pellucid and 

 sweet flesh, fish, and vegetable extracts purer than ever 

 cook manufactured. Three days' exposure to the dusty 

 air suffices to render them muddy, fetid, and swarming 

 with infusorial life. The liquids are thus proved, one and 

 all, ready for putrefaction when the contaminating agent 

 is applied. I invite .my colleague to reflect on these facts. 

 How will he account for the absolute immunity of a 

 liquid exposed for months in a warm room to optically 

 pure air, and its infallible putrefaction in a few days when 

 exposed to dust-laden air? He must, I submit, bow to the 

 conclusion that the dust-particles are the cause of putre- 

 factive life. And unless he accepts the hypothesis that 

 these particles, being dead in the air, are in the liquid 

 miraculously kindled into living things, he must conclude 

 that the life we have observed springs from germs or 

 organisms diffused through the atmosphere. 



The experiments with hermetically sealed flasks have 

 reached the number of 940. A sample group of 130 of 

 them were laid before the Royal Society on January 13, 

 1S76. They were utterly free from life, having been com- 

 pletely sterilized by three minutes' boiling. Special care 

 had been taken that the temperatures to which the flasks 



