THE VITAL PHENOMENA OF BACTERIA. 99 



a certain extent as a poor substitute for pro 

 teid ; gelatin is the lowest substance of the 

 kind utilizable by man. 



The facts of fermentation became in Pas- 

 teur's hands the starting-point for conceptions 

 which later were to revolutionize our way of 

 looking upon the composition of chemical 

 bodies. Pasteur found that in certain fermen- 

 tations there was present, besides the active 

 dextro-rotatory tartaric acid, the so-called active 

 Isevo-rotatory tartaric acid. These two acids 

 combine to form the optically inactive racemic 

 (paratartaric) acid. Pasteur accounted for this 

 by the asymmetric structure of the chemical 

 molecule. Out of this beginning Le Bel and 

 van't Hoff developed the theory of the asym- 

 metric carbon atom and modern stereo-chemis- 

 try. In spite of all the progress that has been 

 made in developing synthetic methods, the de- 

 struction of inactive substances by fermenta- 

 tion and, by that means, the preparation of the 

 optically active components has been held to 

 as a rapid and important method in the domain 

 of organic chemistry and still maintains this 

 position. Schardinger discovered by this 

 method the laevo-rotatory lactic acid which had 

 never before been obtained chemically, and the 

 existence of which was suspected only because 

 the inactive lactic acid and the active dextro- 



