BACTERIA AND THEIR GERMS. 81 
himself that even very thick-coated seeds could 
not resist this destructive agent ; whilst he thought 
that the idea, entertained by some, of the eggs of 
the lowest infusoria being protected from the in- 
jurious influence of the boiling water by reason of 
their extreme minuteness, was a supposition so 
improbable as scarcely to deserve serious con- 
sideration. Such a notion was, he thought, wholly 
opposed to what was known concerning the trans- 
mission of heat. Whilst, therefore, the opinion of 
those who believe that eggs have the power of 
resisting the destructive influence of boiling water 
could be fully refuted, Spallanzani thought it by 
no means followed that the infusoria which always, 
after a very short time, appeared in boiling in- 
fusions had arisen independently of the existence 
of eggs. The infusions being freely exposed to the 
air, it was very possible that this air had intro- 
duced eggs into the fluids, which by their develop- 
ment had given birth to the infusoria.* 
After the lapse of a century it has at last been 
clearly shown that this supposition of aérial con- 
» A few pages further on this view is thus shortly expressed :—“ Il 
est évident que touts les tentatives faites avec le feu, peuvent bien servir 
a prouver que les animaux microscopiques ne naissent point des ceufs que 
l'on supposait exister dans les infusions avant qu’on leur fit sentir le feu; 
mais cela n’empéche pas qu’ils n’aient pu étre formés de ceux qui auront 
été portés dans les vases aprés Vébullition.” 
G 
