The Pharmacology of Pyraconitine and Ifcthylbenzaconinc. 385 



therefore differs in composition from aconitine by the loss of one 

 molecule of acetic acid, and from benzaconine by one molecule of 

 water. 



Methylbenzaconine was obtained from aconitine by heating it with 

 methyl alcohol in a closed tube.* A remarkable reaction takes place, 

 in which the acetyl group is ejected as acetic acid, a methyl group 

 taking its place. This alkaloid therefore differs from aconitine in 

 containing a methyl group in the place of the acetyl group, and from 

 benzaconine in containing a methyl group in the place of one atom 

 of hydrogen. The examination of its physiological action would 

 therefore be the means of studying the result of replacing in aconitine 

 the negative radical acetyl by the positive methyl group, and also of 

 studying the effect of the introduction of methyl in modifying the 

 physiological action of benzaconine. 



The acetyl group of aconitine evidently occupies an exceptional 

 position in the molecule of aconitine. So far as we are aware it is 

 the only acetyl compound at present known, which exchanges this 

 group for methyl when it is heated with methyl alcohol. We have 

 examined the behaviour of numbers of different types of acetyl 

 derivatives from this point of view and can find none analogous to 

 aconitine. 



For the study of their physiological action these alkaloids have 

 been specially purified and employed as hydrobromides in aqueous 

 solution. 



Contrasting the physiological action of pyraconitine with that of 

 aconitine, as described in the present paper, we find, as might be 

 anticipated from our previous results, that through the removal of the 

 acetyl group the great toxicity of aconitine is nearly entirely abolished 

 and the characteristic features of aconitine poisoning are no longer 

 produced by pyraconitine. 



Contrasting the physiological actions of benzaconine and pyr 

 aconitine which differ from each other empirically by one molecule of 

 water, pyraconitine, the anhydride, is the more active compound. 

 Both these alkaloids, divested of the acetyl group of aconitine, are rela- 

 tively weak and feebly toxic when compared with the parent alkaloid. 



Although benzaconine and pyraconine exhibit a strong similarity in 

 the physiological effects they produce, there are differences between 

 them which are probably more considerable than they would be if 

 pyraconitine were merely the anhydride of benzaconine. 



The substitution in aconitine of methyl for acetyl which occurs in 

 the formation of methyl benzaconine has led to a very considerable 

 reduction in toxicity and has introduced a curare-like effect similar to 

 that first o^r^ed by Crum Brown and Fraserf to result from the 



* < Proc. Cliem. Soc.,' 1896, p. 159. 



t ' Trans. Koy. Soc. Edinb.,' 1869, vol. 25, p. 192. 



