560 Proceedings of the Royal Society 
induce them to believe that this analogy is not a very perfect one, 
as the methyl- and ethyl-derivatives of strychnia seem to retain 
a certain degree of the characteristic convulsant action of strychnia.* 
They found, their opinion on the appearance of tetanic spasms in 
the limb of a frog, whose vessels had been ligatured before the 
poisoning, and on the production of coexisting paralysis and con- 
vulsions in mammals poisoned by these substances. Both of these 
effects are obviously explainable by the presence of a minute trace 
of strychnia. In the case of the frog with the vessels of one 
limb tied, the methyl- or ethyl-strychnium salt paralysed all the 
motor nerves to which it had access; but as strychnia was also 
administered, by accident , the excitability of the spinal cord was 
exaggerated, and tetanic spasms therefore occurred in the non- 
poisoned limb — its motor and sensory nerves being protected from 
the paralysing action of the methyl- or ethyl-derivative. The 
appearance of strychnic effects in mammals may likewise he ex- 
plained by the presence of strychnia. One of the authors has 
shown, in a paper communicated to this Society, that when a suf- 
ficient dose of a substance that paralyses the terminations of motor 
nerves is administered to a frog along with a certain proportion of 
one that stimulates the spinal cord, the symptoms are those of 
paralysis alone; but when this combination is administered, in the 
same relative proportions, to a mammal, the symptoms are those of 
paralysis coexisting with convulsions. f This result is sufficient to 
account for the different symptoms observed by Messrs Jolyet and 
Cahours on frogs and on mammals, on the supposition that the 
methyl- and ethyl-strychnium salts they employed contained 
strychnia. 
The authors have made a number of experiments which support 
this supposition. Several specimens of these salts, prepared by 
them, were found to produce such complicated effects as the French 
physiologists describe; but by carefully treating them a second 
time with iodide of methyl or of ethyl they succeeded in removing 
the convulsant action. They have also treated a specimen of iodide 
of ethyl-strychnium that produced strychnic effects, with iodide of 
methyl, and thus obtained a substance whose action was a purely 
* Comptes Rendus, Nov. 2, 1868, p. 904. 
t Proceed. Roy. Soc. Edin. vol. vi. p. 434. 
