ORIGINATION OF LIVING BEINGS. 73 



not made good his views. Well, then, the subject con- 

 tinued to be revived from time to time, and experiments 

 were made by several persons ; but these experiments 

 were not altogether satisfactory. It was found that if 

 you put an infusion in which animalcules would appear 

 if it were exposed to the air into a vessel and boiled 

 it, and then sealed up the mouth of the vessel, so that 

 no air, save such as had been heated to 212°, could 

 reach its contents, that then no animalcules would be 

 found ; but if you took the same vessel and exposed 

 the infusion to the air, then you would get animalcules. 

 Furthermore, it was found that if you connected the 

 mouth of the vessel with a red-hot tube in such a way 

 that the air would have to pass through the tube be- 

 fore reaching the infusion, that then you would get 

 no animalcules. Yet another thing was noticed : if 

 you took two flasks containing the same kind of infu- 

 sion, and left one entirely exposed to the air, and in 

 the mouth of the other placed a ball of cotton wool, 

 so that the air would have to filter itself through it 

 before reaching the infusion, that then, although you 

 might have plenty of animalcules in the first flask, you 

 would certainly obtain none from the second. 



These experiments, you see, all tended towards one 

 conclusion — that the infusoria were developed from little 

 minute spores or eggs which were constantly floating 

 in the atmosphere, which lose their power of germi- 

 nation if subjected to heat. But one observer now made 

 another experiment, which seemed to go entirely the 

 other way, and puzzled him altogether. He took some 

 of this boiled infusion that I have been speaking of, 

 and by the use of a mercurial bath — a kind of trough 

 used in laboratories — he deftly inverted a vessel con- 

 4 



