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1 ' If I had to defend the novelty of the ideas introduced into 

 medicine by my labours of the last twenty years," wrote Pasteur 

 from Arbois in September, 1879, "I should invoke the sig- 

 nificant spirit of Littre's words. Such was then the state of 

 Science in 1836, and those ideas on the etiology of great epi- 

 demics were those of one of the most advanced and penetrating 

 minds of the time. I would observe, contrarily to Littre's 

 opinion, that nothing proves the spontaneity of great epi- 

 demics ! As we have lately seen the phylloxera, imported from 

 America, invade Europe, so it might be that the causes of 

 great pests were originated, unknowingly to stricken countries, 

 in other countries which had had fortuitous contact witfi the 

 latter. Imagine a microscopic being, inhabiting some part of 

 Africa and existing on plants, on animals, or even on men, and 

 capable of communicating a disease to the white race ; if 

 brought to Europe by some fortuitous circumstance, it may 

 become the occasion of an epidemic. ..." 



And, writing later, about the same passage : " Nowadays, 

 if an article had to be written on the same subject, it would 

 certainly be the idea of living ferments and microscopic beings 

 and germs which would be mentioned and discussed as a cause. 

 That is the great progress," added Pasteur with legitimate 

 pride, " in which my labours have had so large a share. But 

 it is characteristic of Science and Progress that they go on 

 opening new fields to our vision ; the scientist, who is exploring 

 the unknown, resembles the traveller who perceives further 

 and higher summits as he reaches greater altitudes. In these 

 days, more infectious diseases, more microscopic beings appear to 

 the mind as things to be discovered, the discovery of which will 

 render a wonderful account of pathological conditions and of 

 their means of action and propagation, of self -multiplication 

 within and destruction of the organism. The point of view is 

 very different from Littre's! ! " 



On his return to Paris, Pasteur, his mind overflowing with 

 ideas, had felt himself impelled to speak again, to fight once 

 more the fallacious theory of the spontaneity of transmissible 

 diseases. He foresaw the triumph of the germ theory arising 

 from the ruin of the old doctrines at the price, it is true, of 

 many efforts, many struggles, but those were of little conse- 

 quence to him. 



The power of his mind, the radiating gifts that he possessed, 

 were such that his own people were more and more interested 



