444 



Mr. S. A. Sworn on the Constitution 



1 



Ladenburg's 

 symbol. 



will give 



2 5 



opening out to 



or 



2 4 



opening out to 



or 



opening out to 



3 z 



The difference may be thus denned : — 



The symbol of Thomsen will give rise to a ring in which 

 each carbon atom is bound to what were in the benzene 

 molecule its ortho-neighbours ; whereas in those derived from 

 Ladenburg's symbol, a carbon atom would in no case be directly 

 attached to atoms which were previously its ortho-neighbours. 



The ascertained constitution of conine helps us to dis- 

 tinguish between these two methods of notation. Conine is 

 undoubtedly the hexahydro-derivative of ortho-propyl pyri- 

 dine. (See especially the researches of Hofmann, Ladenburg, 

 Skraup, and Cobenzl, on conine and picolic acid, described in 

 Pictet's " La Constitution Chimique des Alcalo'ides Vege- 

 taux") 



Its optical activity is due to the presence of an asymmetric 



