YEAST CELL AND ITS LESSONS 173 



would some day have succeeded in making name and fame 

 as a painter." 



It is a legitimate question to ask why Pasteur happened 

 to take up the study of fermentation. The answer affords 

 another of those happy chances which are the salt of 

 scientific life. As a crystallographer he was bent on solv- 

 ing those old problems suggested by the tartaric acids. He 

 noticed how one type of this acid deflects the beam of light 

 to the right, another to the left. Further, he chanced to 

 observe that certain micro-organisms exercise a selective 

 action when sown in these solutions thriving in one, pin- 

 ing in the other. Here then was a clue, for surely the 

 contents of the cells Schwann had declared alive must con- 

 trol such dainty selective action. What followed in those 

 fruitful years it were quite needless for me to recapitulate. 

 Liebig and his molecular oscillations were forgotten by all 

 save the faithful few, and for forty years mankind reveled 

 in the thought that the fermentation of sugar was indis- 

 solubly connected with the life action of a living organized 

 structure. Yet, on the crucial point, Pasteur was in error. 

 It must not be forgotten, however, that by his classical 

 experiments with the isomeric tartaric acids Pasteur 

 practically laid the foundations of stereo-chemistry. The 

 development of this fruitful branch of learning was, neces- 

 sarily, slow at first, and indeed, it was not until 1873 that 

 much headway was achieved. In that year Wislicenus 

 pointed out the deductions of his work on lactic acid, and 

 it seemed clear to men of science that the difference be- 

 tween compounds of identical structure was due to differ- 

 ences in the " arrangement in space" of atoms within the 

 molecule. It is to the further development of this difficult 

 subject, at the hands of Le Bel and van't Hoff, who elabor- 

 ated the theory of the asymmetric carbon atom, that we 

 largely owe our knowledge of the carbohydrates. 



The new century opened with new ideas. A book deal- 

 ing with experimental research on alcoholic fermentation, 

 and relating the results of laboratory experiments dating 



