ORIGINATION OF LIVING BEINGS 59 



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 before reaching 

 the infusion, that then you would get no animalcules. Yet 

 another thing was noticed : if you took two flasks con- 

 taining the same kind of infusion, 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 germination 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 containing the infusion into the 

 mercury, so that the latter reached a little beyond the 

 level of the mouth of the inverted vessel. You see that he 

 thus had a quantity of the infusion shut off from any 

 possible communication with the outer air by being inverted 

 upon a bed of mercury. 



He then prepared some pure oxygen and nitrogen gases, 

 and passed them by means of a tube going from the outside 

 of the vessel, up through the mercury into the infusion ; 

 so that he thus had it exposed to a perfectly pure atmosphere 

 of. the same constituents as the external air. Of course, he 

 expected he would get no infusorial animalcules at all in 

 that infusion ; but, to his great dismay and discomfiture, 

 he found he almost always did get them. 



Furthermore, it has been found that experiments made 

 in the manner described above answer well with most 

 infusions ; but that if you fill the vessel with boiled milk, 

 and then stop the neck with cotton-wool, you will have 

 infusoria. So that you see there were two experiments 

 that brought you to one kind of conclusion, and three to 

 another ; which was a most unsatisfactory state of things 

 to arrive at in a scientific inquiry. 



