36 ORIGIN AND MAINTEN. OF OPT. ACTIVITY 



other asymmetry of the same order of magnitude, i.e., 

 possessing the same degree of optical purity. We shall 

 refer to this view as Curie's principle. 



Emil Fischer (1894), after having stated that "one 

 active molecule gives birth to another," illustrates his 

 statement by the following concrete example : ' ' The for- 

 mation of sugar in plants, according to the observations 

 of physiologists, takes place in chlorophyll grains, which 

 themselves consist of optically active substances." (The 

 optical activity of chlorophyll has been demonstrated 

 recently by Stoll and Wiedemann, 1933.) "I assume," 

 continues Fisher, "that, in the formation of sugar, there 

 is a combination of carbon dioxide or of formaldehyde 

 with these substances of the chlorophyll grains and that 

 the subsequent production of sugar proceeds asymmetri- 

 cally on account of the presence of the asymmetric mole- 

 cules of chlorophyll." Thus Fischer considered chloro- 

 phyll to be an asymmetric catalyst, the asymmetric state 

 of which is transmitted to the molecules of the organic 

 substance undergoing synthesis and these are, therefore, 

 represented by only one optical isomer. The notion of 

 asymmetric synthesis was thus introduced. 



Somewhat earlier, Fischer (1890) had proposed another 

 explanation for the origin of the asymmetric state. He 

 assumed that, in plants, as in the laboratory, racemic com- 

 pounds would appear first and that these would subse- 

 quently be split up by the plant itself into their optical 

 antipodes. 



A few years after Fischer had expressed this opinion, 

 Brown and Morris (1893), in a thorough study of sugar 

 metabolism in plants, could find in them neither racemic 

 nor laevorotatory glucose. This finding caused Fischer 

 to abandon his previous idea. 



It is now well known that laevorotatory glucose does not 

 occur in living organisms, that it practically does not fer- 

 ment and that it is not used as food by plants or animals. 

 Furthermore, a great deal of experimental data has been 

 accumulated which shows that, in different enzymatic re- 



