ORIGIN AND MAINTEN. OF OPT. ACTIVITY 55 



it at the present time, was involved in the early stages of 

 natural selection while Krebs' mechanism, which is more 

 higlily efficient, was developed only later in evolution. 



The asymmetric state of protoplasm and its mainte- 

 nance by regulative mechanisms appear, then, as a heri- 

 tage of countless ages of transformations, and as a result 

 of the elaboration by nature of systems which seem to tend 

 to some sort of physiological perfection. 



SUMMARY 



1. According to the earlier authors, asymmetry, once 

 originated, has been transmitted from one substance to 

 another, as life is transmitted from one living being to 

 another. 



2. Emil Fischer suggested that asymmetric catalysts 

 synthesize asymmetric compounds from symmetric ones. 

 Such asymmetric syntheses were soon realized in labora- 

 tory experiments. 



3. It was then observed that, in an asymmetric synthe- 

 sis, the optical activity reaches a maximum and then 

 decreases, and that the enzyme does not influence the equi- 

 librium constant of the reaction. These observations have 

 been the basis of theoretical investigations by Kuhn on 

 the thermodynamics of asymmetric synthesis. 



4. Kuhn pointed out that the separation of two optical 

 isomers requires an expenditure of work, while their mix- 

 ing into a racemate liberates energy, the optically active 

 state being a state of disequilibrium. He further showed 

 that the characters presented by enzymatic reactions are 

 those thermodynamically expected in true catalysis. 



5. Optical purity might be conditioned in some cases by 

 the behaviour of "stereo-autonomic substances," i.e., of 

 substances whose properties, such as solubility, maintain 

 one isomer in solution while the other separates out. 



6. To maintain the state of disequilibrium inherent in 

 optical purity, nature, it seems, has developed regulating- 

 mechanisms, such as: {a) The use of widely different 

 velocities in the formation of the two optical isomers in 



