332 FRAGMENTS OF SCIENCE 



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 swarm- 

 ing 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 

 putrefactive life. And unless he accepts the hypothesis 

 tbat 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 Eoyal Society on January 13, 

 1876. 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 

 were exposed should include those previously alleged to 

 be efficient. The conditions laid down by the heterogenist 

 were accurately copied, but there was no corroboration 

 of his results. Stress was then laid on the question of 

 warmth, thirty degrees being suddenly added to the tern- 



