308 THE FLOATING-MATTEE OF THE AIR. 



as the creatures of fancy. But I do affirm, not as a 

 ' supposition,' nor an ' assumption,' nor a ' probable 

 guess,' nor as ' a wild hypothesis,' but as a matter of 

 the most undoubted fact, that the spores of the hay 

 bacillus, when thoroughly desiccated by age, have 

 withstood the ordeal mentioned. And I further affirm 

 that these obdurate germs, under the guidance of the 

 knowledge that they are germs, can be destroyed by 

 five minutes' boiling, or even less. This needs explana- 

 tion. The finished bacterium perishes at a temperature 

 far below that of boiling water, and it is fair to assume 

 that the nearer the germ is to its final sensitive condi- 

 tion the more readily will it succumb to heat. Seeds 

 soften before and during germination. This premised, 

 the simple description of the following process will 

 suffice to make its meaning understood. 



An infusion infected with the most powerfully re- 

 sistent germs, but otherwise protected against the 

 floating matters of the air, is gradually raised to its 

 boiling-point. Such germs as have reached the soft 

 and plastic state immediately preceding their develop- 

 ment into bacteria are thus destroyed. The infusion is 

 then put aside in a warm room for ten or twelve hours. 

 If for twenty-four, we might have the liquid charged 

 with well-developed bacteria. To anticipate this, at 

 the end of ten or twelve hours we raise the infusion a 

 second time to the boiling temperature, which, as 

 before, destroys all germs then approaching their point 

 of final development. Tlie infusion is again put aside 

 for ten or twelve hours, and the process of heating is 

 repeated. We thus kill the germs in the order of 

 their resistance, and finally kill the last of them. No 

 infusion can withstand this process if it be repeated a 

 sufficient number of times. Artichoke, cucumber, and 

 turnip infusions, which had proved specially obstinate 



