194 THE FLOATING-MATTER OF THE AIR. 



thus executed, the results of which distinctly favoured 

 the conclusion, though they did not to my satisfaction 

 prove it, that the resistant germs were not to be wholly 

 ascribed to the air, but that they had survived in the 

 liquid. 



§ 19. Final proof that the Resistant Germs are em- 

 braced by the Infusion. Examples of Resistance 

 both in Acid and Neutral Liquids, 



We here face a question which greatly harassed 

 me at the time to which I now refer. It was this: — 

 Have the germs, which under the circumstances here 

 described produced life, been really embraced by the 

 infusion itself during the time of heating? The liquid, 

 it will be remembered, had to pass through the neck 

 of the pipette-bulb, and it could not descend from the 

 neck into the bulb without leaving a film adherent to 

 the internal surface of the neck. This film, I reflected, 

 might dry in part by evaporation ; and it might, in doing 

 so, leave germs behind which would be very differently 

 circumstanced from those in the liquid. To germs thus 

 exposed, not to the heat of water, but to the possibly 

 less effective heat of vapour and air, the observed life 

 might I thought be due. Before closing definitely with 

 the proposition that the surviving germs had actually 

 been in the liquid, the possibility to which I have just 

 referred had to be inexorably shut out. 



The evil was to some extent mitigated by charging 

 the bulb, not through its own neck, but through a 

 narrow tube issuing at right angles to the neck. But 

 even here a portion of the neck and of the higher 

 interior surface of the bulb was trickled over by the 

 infusion. The difficulty was finally met, and completely 

 surmounted, by causing the lateral tube to issue from 



