THE WORK OF PASTEUR 3I 



and blood for an indefinite time without submitting them 

 to heat or any other treatment. It is only necessary to with- 

 draw them from the body of the animal, ^vhere they do not 

 contain bacteria, ^vhile taking precautions against contamina- 

 tion with germs from outside. Under these circumstances 

 such liquids do not putrefy and may be conserved in- 

 definitely. 



Pasteur did not merely aim at getting accurate and uniform 

 results but also at explaining the contradictory data of other 

 authors. He rejected the suggestion that decaying infusions 

 give rise to microbes and showed that, on the contrary, the 

 decay of these liquids itself takes place as a result of the 

 vital activities of micro-organisms which have entered from 

 outside. All attempts to refute this hypothesis and to find a 

 case of spontaneous generation of any particular organism 

 were in vain. From our present point of view this is quite 

 understandable, in that micro-organisms are not simple lumps 

 of organic material as was believed until the time of Pasteur. 

 A detailed study of these very simple living things has shown 

 that they have a very delicate and complicated organisation. 

 It is quite impossible to suppose that complicated structures 

 of this sort could emerge in the course of a short time before 

 our eyes out of structureless solutions of organic substances. 

 This hypothesis is, in essence, just as absurd as the hypothesis 

 that frogs arise from the dews of May or lions from the stones 

 of the desert. 



Pasteur's investigations quite understandably attracted tre- 

 mendous attention among his contemporaries. The complete 

 revolution in biology brought about by Pasteur may be com- 

 pared with that achieved by Copernicus in astronomy. For, 

 in the one case as in the other, prejudices which had held 

 sway over the minds of men for thousands of years were swept 

 away. 



As we have seen above, many generations of scientists and 

 philosophers considered the possibility of spontaneous genera- 

 tion to be an incontrovertible and self-evident truth. The 

 obdurate struggles bet^veen idealism and materialism were 

 only concerned ^\'ith the theoretical explanation of the 

 * phenomenon '. And now it was suddenly discovered that 

 the ' phenomenon ' itself, the very ' fact ' of spontaneous 



