air which has been heated or filtered through cotton.
There are those exceptions which haunted the mind of
Helmholtz, of Schroeder and Dusch, and made them
admit that there were some 'decompositions of organic
matter which needed only the presence of oxygen to
start them,' that is to say that spontaneous generation
was alone capable of explaining. Very well, there again
spontaneous generation has nothing to do with it.
Only carry up to 110° C. your milk, your yolk of egg,
your meat, and you will preserve them intact as easily
as the bouillon. The milk needs to be heated a little
more, and that is all there is to it. It is not that it
contains more resistant germs, but that it is slightly
alkalin, and in an alkalin medium germs are more resist-
ant to the action of heat. The proof is that a decoction
of yeast, which is easily sterilized by a short boiling at
100° C. when it is slightly acid, needs to be heated to
105° C. or 110° C. when there is added to it a small
amount of carbonate of lime. It behaves then like the
milk."

We shall see later that there is in the interpretation of
this experiment an error brought to light by Bastian,
but which did not invalidate the conclusion, for Pasteur,
when he was deceived, had the art of never being deceived
more than half way. He approached the mark, when he
did not hit the bull's-eye. We shall find a new example of
this in the complementary demonstration which follows.

There was in favor of spontaneous generation one last
argument to which Pasteur had not yet replied. It is
the experiment to which we have referred, in which Gay-

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