126 ASYMMETRIC ANALYSIS 



strength i^reseuted a considerable increase in the rate of 

 movement. The left isomer of cinchonine definitely call- 

 ed forth at first a strong stimulation of movement; sub- 

 sequently the motion slowed down and finally the para- 

 mecia died. With the right cinchonine the stimulation 

 phase was entirely absent under all concentrations em- 

 ployed, only the inhibition phase could be observed. 



So only the laevorotatory isomer has the specific power 

 of stimulating the ciliary movement. One can suppose 

 that the left isomer, because of peculiarities of its spatial 

 configuration, interacts with the system of reactions 

 which control the ciliary motion, while this system re- 

 mains as if "closed" for the dextrorotatory isomer. In 

 distinction from this stimulating effect, the less specific 

 process of toxic destruction of the locomotory force of 

 the cilia is carried out qualitatively in the same way by 

 both optic isomers of cinchonine, the rate of the reaction 

 only is different. This situation has its parallel in the 

 following observation of Krebs (1936). He has recently 

 pointed out that in the metabolism of amino acids some 

 specific transformations such as the splitting of the imi- 

 dazole ring in histidine (Edlbacher and Neber, 1934), or 

 the oxidation of the ring in tyrosine (Bernheim, 1935), 

 are open only to the natural amino acids of the left series 

 and are closed for the right forms. On the contrary, in 

 other less specific reactions, such as deamination, both 

 optic isomers of amino acids can participate. 



Further data on the action of optical isomers of cin- 

 chonine upon various protozoa are given in the orig- 

 inal paper by Gause, Smaragdova and Alpatov (1938). 



SUMMARY 



1. The study of the mechanism of various biological 

 processes by examining how they are influenced by opti- 

 cal isomers of various substances is presented as a 

 method of investigation called '^ Asymmetric analysis." 

 This method is applied here in the study of (1) the 



