mmense
number of minute things which could be obtained apparently almost at
will from decaying vegetable and animal forms. Thus, if you took some
ordinary black pepper or some hay, and steeped it in water, you would
find in the course of a few days that the water had become impregnated
with an immense number of animalcules swimming about in all directions.
From facts of this kind naturalists were led to revive the theory
of spontaneous generation. They were headed here by an English
naturalist,--Needham,--and afterwards in France by the learned Buffon.
They said that these things were absolutely begotten in the water of
the decaying substances out of which the infusion was made. It did not
matter whether you took animal or vegetable matter, you had only to
steep it in water and expose it, and you would soon have plenty of
animalcules. They made an hypothesis about this which was a very fair
one. They said, this matter of the animal world, or of the higher
plants, appears to be dead, but in reality it has a sort of dim life
about it, which, if it is placed under fair conditions, will cause it
to break up into the forms of these little animalcules, and they will go
through their lives in the same way as the animal or plant of which they
once formed a part.

The question now became very hotly debated. Spallanzani, an Italian
naturalist, took up opposite views to those of Needham and Buffon, and
by means of certain experiments he showed that it was quite possible 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; bu