160 THE FLOATING-MATTER OF THE AIR. 



a trace of the scum which loaded the infusion outside. 

 2. Eed fungus : one of the three tubes became thickly- 

 turbid, while the two others maintained their pristine 

 brilliancy. 3. Tree fungus : one of the tubes became 

 thickly turbid, the two others remained permanently clear. 



I asked myself why should one tube of the red-fungus 

 give way and the others remain intact ? The answer 

 seemed at hand. The turbid tube had been boiled for 

 only five minutes, while the clear ones had been boiled 

 for ten. On consulting the adjacent chamber this pos- 

 sible explanation was blown to the winds, for here the 

 turbid tube had been boiled for ten minutes, while its 

 untainted neighbour had been boiled for only five. 



Thus, although the more careful repetition of the 

 experiments did not secure every tube from infection, 

 the escape of seven out of nine tubes entirely destroys 

 the presumption of spontaneous life-development which 

 the first experiments might suggest to some minds. 



Wishing to observe more attentively the action of 

 common uncleansed air upon boiled fungus-infusions, a 

 tray of 100 tubes was charged with them on the 14th 

 of October. Thirty-five tubes were filled with black, 

 thirty-five with yellow, and thirty with red-fungus in- 

 fusion. On the 16th of October every one of the yellow- 

 fungus tubes was turbid and covered with a thick, cohe- 

 rent, cobweb-like scum. The surfaces of the black- 

 fungus tubes were also sprinkled with spots of white 

 scum. Turbidity was the only change observed in the 

 red-fungus tubes. They were wholly free from scum. 



Examined microscopically on the 2nd of November 

 the yellow-fungus tubes were for the most part found 

 swarming with exceedingly small and active Bacteria ; 

 the red-fungus tubes also swarmed with Bacteria, some 

 beaded Vibrios being mingled with them. In many of 

 the tubes examined galloping monads appeared, attain- 



