56 ORIGIN AND MAINTEN. OF OPT. ACTIVITY 



asymmetric syntheses; (b) The succession of reactions 

 which are interrupted before the optical activity has had 

 time to disappear (Langenbeck and Triem's mechanism) ; 

 (c) The more rapid deamination of the unnatural isomer 

 which then separates out (Krebs' mechanism). 



7. Optical purity seems to impart to protoplasm some 

 advantages in natural selection, in particular, it seems to 

 increase the reaction rate and the growth activity. So, the 

 establishment of a state of optical purity can be con- 

 sidered as a method used by nature to stabilize the inter- 

 nal milieu. 



8. The origin of asymmetry has been ascribed by 

 several authors to the influence, on some reactions, of 

 circularly polarized light, which would be predominantly 

 right or left on account of its rotation by terrestrial mag- 

 netism ; other authors think that the equality of right and 

 left isomers is a statistical mean value and that the 

 inequality resulted from fluctuations from the mean. 



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