HERMANN VON HELMHOLTZ 



gave his mind the aesthetic bias so apparent in after 

 years. His researches, however, were not anatomical, 

 but physiological and physical. 



In 1843 h mac le an important contribution to the 

 theory of fermentation. This process has long been, 

 and indeed still is, the cause of much controversy 

 between chemical physicists and biologists, and from 

 the controversy has flowed results of the highest 

 importance to humanity. When sugar is changed 

 into alcohol and carbonic acid in the ordinary alcoholic 

 fermentation, the process is in some way related to 

 the vegetable cells of the yeast plant, Saccharomycetes 

 cerevisits, first seen by Leeuwenhoek in 1680. For 

 many years these minute organisms received little or 

 no attention, but in 1838 Schwann, one of the 

 founders of the cell theory, and Cagniard de la Tour 

 demonstrated the vegetable nature of these yeast cells, 

 and showed that they grew and multiplied in saccharine 

 solutions. For the first time it was asserted that 

 fementation in some way depended on the action of 

 living things. Previous to 1838 Berzelius suggested 

 that the action of the yeast is what is called catalytic, 

 that is causing a separation or decomposition of the 

 atoms forming the sugar in a way similar to the 

 action of platinum black on peroxide of hydrogen, 

 when the latter gives up an atom of hydrogen. 

 Liebig strongly contended that there is no necessary 

 connection between the fermentive process and the 

 development of living organisms, and he held that the 

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