Pasteur on Specificity of Disease

Pasteur foresaw the consequences of his studies, and wrote in his book on beer  

When we see beer and wine subjected to deep alterations because they have given refuge to micro-organisms invisibly introduced and now swarming within them, it is impossible not to be pursued by the thought that similar facts may, must, take place in animals and in man. 

It was obvious from Pasteur s studies that each special kind of fermentation or disease of beer or wine was the result of the growth and activity in it of a special, distinct form of yeast or other microorganism, depending on the type of fermentation or disease under investigation. This furthered an idea, already old, of the specificity of biological action, and supported the view that animal and human diseases also, like different sorts of putrefaction and fermentation, were each caused by a single, specific type of microorganism. 

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