120 AswiMtyriiw A\ALysii<i 



The limits of error in measuring the coefficient a may 

 extend over a rather wide range. Thus the following 

 values were obtained in two independent measurements : 

 in Nais 2.57 and 2.25; in Liwiwdrilus 2.9 and 4.0; in 

 Aelosoma variegaium 1.79 and 1.74; in Aelosoma Jiem- 

 prichi 1.50 and 2.18. Nevertheless the order of magnitude 

 of the average is significant. We find nearly the same value 

 in invertebrates (2.6) and in vertebrates (2.8). 



The data above mean that the Protozoa, Coelenterata, 

 Turbellaria, Rotatoria and Nemertinea are deprived of 

 the spatially specific receptive substance which responds 

 differentially to the left isomer of nicotine. Annelides, 

 Chaetognatha and Vertebrates possess this receptor, 

 while in Arthropoda it is absent again. 



2. The Acetylcholine System and the Dlfferottial Ef- 

 fect of the Optical Isomers of Nicotine. Considering that 

 it is the nervous system in animals which is affected by 

 nicotine and that there is an identity of stereo-coeffi- 

 cient in invertebrates and in vertebrates, in spite of es- 

 sential differences in the morphology of their nervous 

 system, we come to the conclusion that there is some 

 uniform receptive substance distributed in the various 

 nervous systems of these animals. However, this chem- 

 ical constituent is not an obligatory component of every 

 nervous system; even some quite differentiated nervous 

 systems of lower invertebrates (Turbellaria and Nemer- 

 tinea) are deprived of it. 



A study of the present views on the mechanism of nic- 

 otine toxic action will furnish more information on the 

 nature of the receptive substance. Thomas and Franke 

 (1924, 1928, 1933) have shown that it is the paralysis of 

 the peripheral neuro-muscular junctions of the respira- 

 tory muscles which is the cause of death of higher ani- 

 mals in acute nicotine poisoning. This view was con- 

 firmed by Gold and Brown (1935). We are thus led to 

 the old classical observations of Langley (1904) that in 

 the ''neuro-muscular junction" there is a certain sensi- 



