70 O FT. A CTIY., HEREDITY AND ENVIRONMENT 



ing pages substances of different optical signs result from 

 the action of optically active catalysts of different signs. 

 One of the two inverse catalysts might have originated by 

 an inverson from the other, but another possibility is that 

 the original catalyst has been changed chemicall}^ so as 

 to produce an optically inverse substance without being 

 itself inverted. The following case illustrates this last pos- 

 sibility. In the study of the enzymatic hydrolysis of 

 racemic ethyl mandelate by the esterase of the human 

 liver, it has been found that if one adds some strych- 

 nine, one obtains a strongly laevorotatory mandelic acid 

 instead of the usual dextrorotatory one (Bamann and 

 Laeverenz, 1930). Strychnine does not influence the vel- 

 ocity of hydrolysis of the right ether, but it strongly in- 

 creases that of the left ether thus causing the formation 

 of an excess of laevorotatory material (for further de- 

 tails see Rona and Amnion, 1933). There was no optical 

 inversion of the enzyme but the chemical properties of 

 the latter have been changed by combination with strych- 

 nine. 



e. C o n t r o 1 of the Production of Op- 

 tical Isomers by Intermediate * ' P a t h- 

 w ays ". Let us now consider in greater detail the case 



TABLE 15 



Optical Pkoperties of the Nitriles Synthesized from Hydrocyanic 

 A( ID AND VAiiioiw Aldehydes undei: the Action of Different 



Organic Catalysts 



