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AMINATION OF PASTEUR’S DOCTRINES 119 


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of thoroughness shown by him in seeking to inter- 
pret the different results met with. 
The sub-title of his celebrated memoir of 1862 
was, “Examen de la Doctrine des Génerations 
Spontanées,” and the first twenty pages of it were 
historical in nature, in which he discussed the ex- 
J periments of Needham and Spallanzani pretty fully, 
az and then those of Schwann and some other workers. 
His own researches had led him to believe that 
‘“ferments ” were not albumenoid substances under- 
going a peculiar though little-known change, as 
Liebig had taught. According to Pasteur (oc. cz¢., 
p. 23) mere albumenoid substances, ‘ n’étaient 
jamais des ferments, mais l’aliment des ferments. 
Les vrais ferments étaient des étres organises.” 
But it was impossible to establish this doctrine, or 
to attempt to establish it, except by rebutting the 
evidence which seemed to tell in favour of 
“spontaneous generation.” 
If, in such experiments as those he had been dis- 
cussing, prepared after the manner of Needham and 
Spallanzani or after that of Schwann, the heating 
had been adequate and the subsequent protection 
from contamination had been perfect ; and if, never- 
theless, organisms appeared within the experimental 
vessels, Pasteur ought to have known quite as well 
as either of these other experimenters, that if it 
could not be shown by dzrect experiments that the 
previous heating had been inadequate to destroy all 
pre-existing life within the vessels, the rival inter- 
pretation must be admitted, as Spallanzani fully 
recognised—namely, that there had been a ae novo 
