204 THE FLOATING-MATTER OF THE AIR. 



cases just recorded, where single bulbs escaped steriliz- 

 ation though exposed for five, six, and eight hours to 

 the boiling temperature, it was always a neutral bulb 

 that kindled into life. To these instances another may 

 be added here. On the 22nd of March an infusion of 

 the wiry Gruildford hay already referred to was divided 

 into two parts, one of which was neutralized and the 

 other left acid. Five pipette-bulbs were filled with the 

 one infusion and five with the other. After hermetic 

 sealing they were all completely submerged in water 

 and boiled for six hours. Every one of the acid bulbs 

 was sterilized by this process, while in two days three 

 of the five neutral ones became turbid and covered with 

 scum. 



The best thought that I have been able to bestow 

 upon this subject does not induce me to lean towards 

 the explanation suggested by M. Pasteur, namely, that 

 the germs escape the destructive action of the heat 

 because they are not wetted by the alkaline or neutral 

 liquid. From the comparative action of alkalized and 

 acidulated water upon hay, I should be inclined to infer 

 that the wetting of its germs by the former would be 

 more prompt than by the latter. The question, I think, is 

 not one of wetting, but of relative nutritive power. Two 

 Bactei^a-germs of equal vital vigour dropping from the 

 atmosphere, the one into a neutral or slightly alkaline, 

 the other into an acid infusion, soon cease to be equal 

 in vigour. The life of the one is promoted, the life of 

 the other only tolerated by its environment. When 

 the temperature surrounding both is raised to a pre- 

 judicial height the one will suffer more than the other, 

 because equally inclement conditions are brought to 

 bear upon constitutions of different strengths; and if 

 the temperature be sufficiently exalted or sufficiently 

 prolonged to become fatal, the more weakly organism 



