Highlights in the History of Microbiology 33 



Schwann (1810-1882) in 1837, and Friedrich Kiitzing (1807- 

 1893) in 1837 independently reported that yeasts play a role in 

 the process o£ fermentation. Witnessing budding in veast water, 

 Charles Cagniard-Latour ( 1777-1859 ) referred to these objects 

 as livino; substances. Ferments, as far as he was concerned, were 

 composed of cells susceptible to reproduction by a sort of budding 

 process, and these living objects were capable of acting upon 

 sugars through "some effect of their vegetation." Schwann des- 

 cribed yeasts as vegetative germs. These adherents of a biological 

 theory to explain fermentation were scorned by most scientists of 

 their day because the biological explanation was in direct con- 

 tradiction to the physico-chemical theory of that renowned German 

 organic chemist, Justus von Liebig (1803-1873). Von Liebig held 

 sway from 1840-1860, and few individuals dared to question his 

 decisions. When he announced that microbes were not the cause 

 of fermentation, his faithful followers went along with the idea 

 and helped to perpetuate the untruth. Molecules are in a constant 

 state of motion— are chemically unstable— according to von Liebig, 

 and when small amounts of decomposing stuff are mixed with fresh 

 fermentable material, a chain-like reaction is initiated and continues 

 until the fermentation is complete. Fermentation was believed to 

 be a natural physical decomposition of large molecules with bacteria 

 and other organisms capitalizing on this more readily available food 

 supply for their metabolism. This supported the concepts of 

 Georg Stahl (1660-1734) expressed in 1697 when he suggested 

 that the process of fermentation was the result of the shattering 

 of molecules by forces either from within or from without. Just 

 what set off the reaction was never made quite clear by any of the 

 proponents of the mechanistic theory. In 1869 when Berzelius, 

 the renowned Swedish chemist of Upsala, supported the mechan- 

 istic approach with his explanation that it was due to contact of 

 catalytic forces, things looked dark for the opponents. 



The genius of Louis Pasteur arrived on the scene in time to set 

 up one of the more famous controversies in microbiology: Pasteur's 

 biological vs. von Liebig's mechanistic theory of fermentation. 

 Believing that the proof of such knotty problems lay in the experi- 



