ible to
stop the process by boiling the water, and closing the vessel in which
it was contained. "Oh!" said his opponents; "but what do you know you
may be doing when you heat the air over the water in this way? You may
be destroying some property of the air requisite for the spontaneous
generation of the animalcules."

However, Spallanzani's views were supposed to be upon the right side,
and those of the others fell into discredit; although the fact was
that Spallanzani had not made good his views. Well, then, the subject
continued 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 degrees, 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
before 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 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 communicat