THE QUESTION OF SPONTANEOUS GENERATION. 91 



wise explain their presence and rapid multiplication 

 in all dead animal or vegetable matter in process of 

 decomposition ? ' 



Buffon lent the authority of his name to the doc- 

 trine of spontaneous generation. He even devised 

 a system to explain this hypothesis. In 1745 two 

 ecclesiastics entered upon an eager controversy for 

 and against this question. While the English Catholic 

 priest Needham adopted the theory of spontaneous 

 generation, the Italian priest Spallanzani energetically 

 opposed it ; but while in the eyes of the public the 

 Italian remained master of the dispute, his success was 

 more apparent than real, more in word than in deed. 



The problem was again brought forward in a more 

 emphatic manner in 1858. M. Pouchet, director of 

 the Museum of Natural History at Eouen, in address- 

 ing the Academy of Sciences, declared that he had 

 succeeded in demonstrating in a manner absolutely 

 certain the existence of microscopic living organisms, 

 which had come into the world without germs, and 

 consequently without parents similar to themselves. 



How came Pasteur to throw himself into this dis- 

 cussion, at first sight so far removed from his other 

 occupations? The results of his researches on fer- 

 mentation led him to it as a sort of duty. He was 

 carried on by a series of logical deductions. Let us 

 recall to mind, for example, the experiment in which 

 Pasteur exposed to the heat of the sun water sweetened 



