86 LOUIS PASTEUR 



that maggots do not arise spontaneously, but de- 

 velop from eggs laid by flies. 



Other naturalists extended these observations 

 and experiments, and finally banished from science 

 the notion that such creatures as worms, insects, 

 fishes or frogs arise spontaneously. Closer investi- 

 gation of the life history of these forms revealed 

 the fact that they arise from eggs of members of 

 their own species. To-day nothing could seem 

 more incredible to a trained biologist than that an 

 angleworm or an insect should arise by a process 

 of spontaneous generation. He would as soon 

 expect that a Westminster Abbey should sud- 

 denly build itself out of the paving stones of the 

 street. 



With our present knowledge, we easily perceive 

 that the older notions of spontaneous generation 

 were exceedingly crude. In the light of the scien- 

 tific knowledge that accumulated during the seven- 

 teenth and eighteenth centuries, it was impossible 

 for them long to persist. But when the compound 

 microscope revealed myriads of minute living crea- 

 tures in a drop of stagnant water, the question of 

 spontaneous generation presented itself anew. That 

 these strange simple organisms might arise by a 

 transformation of organic matter was a conclusion 



