

’ hd 
EXAMINATION OF PASTEUR’S DOCTRINES 121 
which Pasteur said, “I have certainly had occasion 
to repeat the experiment more than fifty times, and 
in no case has this fluid, otherwise so changeable, 
shown a vestige of organism when in the presence 
of calcined air.” But after a time Pasteur began to 
employ an entirely different fluid, and in all these 
experiments living organisms were invariably present 
in the previously boiled liquids, just taken from 
newly opened flasks. Formerly he used ‘“l’eau de 
leviire sucrée,” but now he employed milk—a much 
more complex and more highly nutritive fluid. After 
further experiments with this and other neutral 
fluids he came to the conclusion that living organisms 
might be encountered in almost any suitable neutral 
or slightly alkaline fluid, which had been submitted to 
Schwann’s conditions ; though, on the contrary, they 
were not to be met with when the solutions employed 
had an acid reaction. 
Whatever fluids are used, if, after they have been 
boiled and exposed to a given set of conditions, 
organisms are not found, their absence would be 
explicable in one or other of two ways. Either the 
heat has proved destructive to all living things in 
these solutions; or else the particular conditions to 
which the organic matter in these solutions has been 
exposed have been such as to prevent the occurrence 
of fermentative changes. Any person wishing to 
ascertain the truth, and competent to deal with such 
a subject, could not fail to see that he was bound to 
give equal attention to each of these possibilities, 
He would have no right to assume that the proba- 
bilities were greater in favour of the one mode of 
