CHEMICAL CONSTITUTION AND PHYSIOLOGICAL ACTION. 193 



rectly connected with our present subject. When, however, we compare the 

 activity of the sulphates of the majority of the ammonium bases considered in 

 this paper with that of the corresponding iodides, we observe striking differences, 

 which cannot be explained by differences of solubility alone, but which, we 

 believe, must be also due to the remarkable stability possessed by these iodides. 

 Strychnia is a much less soluble substance than iodide of methyl-strychnium, 

 and yet a rabbit that survived the administration of fifteen grains of iodide 

 of methyl-strychium, was killed in a few minutes by the administration of one- 

 twentieth of a grain of strychnia. Before absorption, the strychnia may have 

 been converted into a more soluble form, and this change may have facilitated its 

 absorption, and permitted it to be carried by the blood-stream to the tissues it 

 affects ; but the great stability of the iodide of methyl-strychnium prevents its 

 conversion into a more soluble form, and so impedes greatly the absorption. Just 

 a s in the more familiar case of the salts of lead, the sulphate is inert while the 

 carbonate is poisonous, although they are both insoluble ; and this difference 

 of physiological action is undoubtedly due to the fact, that the carbonate, on 

 account of its instability, is readily converted in the stomach into a soluble salt, 

 while no such change takes place in the case of the sulphate. Stability may 

 also influence the physiological activity of these iodides, even after their absorp- 

 tion, by preventing those chemical actions on the tissues by which many of 

 the effects of poisons are probably caused. 



The change in the character of the physiological action is remarkably illus- 

 trated by strychnia, brucia, and thebaia, whose purely spinal-stimulant action is 

 converted into a paralysing action on the periphery (end-organs) of motor nerves ; 

 it is apparent in codeia and morphia, whose convulsant action is also converted into 

 a paralysing action on motor nerve end-organs, and whose hypnotic action is 

 apparently altogether destroyed in the case of codeia, and certainly greatly 

 diminished in that of morphia ; and it is obviously, though less so than with the 

 others, in the case of nicotia, whose convulsant action is diminished if not alto- 

 gether removed. We may conclude from these facts, that when a nitrile base 

 possesses a strychnia-like action, the salts of the corresponding ammonium bases 

 have an action identical with that of curare. 



It is well known that curare and strychnia are derived from plants belong- 

 ing to the same genus, and it is, therefore, interesting to observe such a 

 relationship. It may not, however, be altogether superfluous to add, that 

 strychnia, brucia, and the other spinal-stimulant alkaloids examined in this 

 paper, have not been converted by chemical addition into curarina, — the 

 active principle of curare. The action of the methyl derivatives of these 

 bases is of precisely the same character as that of curare, and they possess the 

 same peculiarity of slow absorption by the mucous membrane of the digestive 

 system, but the degrees of their activity are very different. If we confine our 



