210 THE FLOATING-MATTER OF THE AIR. 



dies of hay hung up for seven or eight weeks in the hot 

 rooms of the Turkish Bath in Jermyn Street, and ex- 

 posed during the whole of this time to a temperature 

 of 1 40° Fahr. and upwards. The germs adherent to this 

 hay were not killed by even this amount of desiccation. 

 When a sterilized animal or vegetable infusion was 

 infected with them they gave birth in the usual time 

 to swarms of Bacteria. 



§ 22. Sterilization by discontinuous Heating, 



Keeping the distinction between germs and de- 

 veloped organisms here insisted on, and the probable 

 changes that occur in passing from the one to the other, 

 clearly in view, I have been able to sterilize with in- 

 fallible certainty the most obstinate infusions referred 

 to in this paper, without either raising the tempera- 

 ture of the infusions beyond their ordinary boiling- 

 point, or inordinately prolonging the application of 

 heat. The infusions may be sterilized by a tempera- 

 ture even below that of boiling water, while the time 

 of its application may be but an extremely minute 

 fraction of that resorted to in some of the foregoing 

 experiments. 



It is an undisputed fact that active Bacteria are 

 killed by a temperature far below that of boiling water. 

 It is also a fact that a certain period, which I have 

 called the period of latency, is necessary to enable the 

 hardy and resistant germ to pass into that organic con- 

 dition in which it is so sensitive to heat. There can 

 hardly be a doubt that the nearer the germ approaches 

 the moment when it is to emerge as the finished organ- 

 ism, the more susceptible it is to that influence by 

 which that organism is so readily destroyed. We may 

 learn from experience, aided by the power of search 



