word in the sense in which we now employ it, he
only meant to say that every living thing originated in a little rounded
particle of organized substance; and it is from this circumstance,
probably, that the notion of Harvey having opposed the doctrine
originated. Then came Redi, and he proceeded to upset the doctrine in a
very simple manner. He merely covered the piece of meat with some very
fine gauze, and then he exposed it to the same conditions. The result
of this was that no grubs or insects were produced; he proved that the
grubs originated from the insects who came and deposited their eggs in
the meat, and that they were hatched by the heat of the sun. By
this kind of inquiry he thoroughly upset the doctrine of spontaneous
generation, for his time at least.

Then came the discovery and application of the microscope to scientific
inquiries, which showed to naturalists that besides the organisms which
they already knew as living beings and plants, there were an immense
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 poss