ASYMMETRIC ANALYSIS 103 



The lower part of Figure 11 represents the data on the 

 toxicity of dextrorotatory and laevorotatory nicotines 

 for Leuciscus, plotted in the manner just indicated. It is 

 evident that the slopes of the straight lines, characteriz- 

 ing the dynamics of the increase of toxicity with concen- 

 tration, are identical. It is therefore reasonable to con- 

 clude that in these experiments the mechanism of killing 

 action in the two optical isomers of nicotine is identical 

 in the sense defined. The unnatural dextro nicotine is 

 weaker only in the sense that a higher dose is required to 

 attain killing. Similar results were obtained also in ex- 

 periments with birds {Acanfhis flammea), lizards {La- 

 certa viridis) and tadpoles {Bana temporaria). Xo dif- 

 ference in the symptoms of poisoning by the two optical 

 isomers was observed. 



Investigations were then carried out to determine the 

 temperature coefficients of toxicity of dextrorotatory and 

 laevorotatory nicotine for various animals. It is known 

 that if one plots the logarithms of the killing rate against 

 reciprocals of absolute temperature, one usually obtains 

 a linear relation. The slope of this straight line is gen- 

 erally represented by |li, which is known as the tempera- 

 ture characteristic (cf. Crozier, 1924). This characteris- 

 tic shows how the killing process is speeded up by the 

 rise of temperature. Physiological processes of differ- 

 ent nature, i.e., in which ditferent mechanisms are at play, 

 usually possess different temperature characteristics. 



The temperature characteristics of toxicity for tadpoles 

 and for the fish Leuciscus were determined according to 

 the following procedure. Two solutions of dextro and 

 laevo nicotines were placed in a constant temperature 

 bath. After the temperature equilibrium was attained, a 

 number of fish or of tadpoles were immersed in the ves- 

 sels and the killing time was recorded. Figure 12 shows 

 the killing rate ( a value inverse to the killing time in 

 seconds) in the fish Leuciscus, due to the action of optic 

 isomers of nicotine at ditferent temperatures, Approxi- 



