CHEMICAL CONSTITUTION AND PHYSIOLOGICAL ACTION. 723 



it was found that its motor conductivity was completely suspended — galvanism 

 of its trunk causing no contractions in the left posterior extremity ; while its 

 sensory conductivity was retained— galvanism causing energetic reflex movements 

 in the right (non-poisoned) posterior extremity. The heart was now contracting 

 twenty-four times in the minute ; and the contractility of the striped muscles was 

 apparently unimpaired. It was possible to excite reflex movements in the right 

 posterior extremity by stimulating the skin of the poisoned region, until one hour 

 and forty minutes after the administration. Very soon after this time, the 

 activity of the reflex function was completely suspended. Irritation of the skin 

 in the poisoned and non-poisoned regions, as well as galvanic stimulation of 

 the poisoned (left) sciatic nerve, caused no movement, notwithstanding that the 

 non-poisoned (right) sciatic nerve and muscles, and even the trunk of the right 

 sciatic nerve above the position of the ligatures, retained their functional activity. 



These two experiments are selected from nine which were made on frogs with 

 different relative doses, and in which distinct evidence was obtained of the 

 primary cause of the paralysis. The conductivity of the motor nerves was 

 suspended before the reflex function was abolished in experiments in which doses 

 were administered, equivalent to the ^yth, the g-^th, the -^oth, the 10 ] bo thi 

 and the 11 1 00 th of the weight of the frog employed ; while the activity of the 

 reflex function was abolished before the motor nerves were paralysed in experi- 

 ments in which doses were administered, equivalent to the T^Vsth, the x^Vo^h. 

 the xeVoth, and the -3 (jWd of the weight of the frog. 



The details we have narrated of Experiments LXXXVIII. and XCI. demon- 

 strate that paralysis of the motor nerves is due to an action on their peripheral 

 terminations ; as well when this paralysis precedes the abolition of the reflex 

 function, as when it occurs subsequently thereto. It would appear that the 

 abolition of the reflex function depends, at least in part, on an action on the spinal 

 cord ; for these experiments show that, after its occurrence, irritation of the skin 

 of a region protected from the direct action of the poison, or galvanic stimulation 

 of the trunk of a mixed nerve likewise protected from the direct action of the 

 poison, does not cause any reflex movement, notwithstanding that the motor 

 nerves and muscles everywhere retain their functional activity. 



We have accordingly shown that conia and methyl-conia produce very similar 

 symptoms ; the more prominent of which are spasms and paralysis. 



Our analysis of the mode in which the paralysis is produced, has resulted in 

 proving its dependence on an action on the motor nerves and on the spinal cord. 

 The rate at which each of these actions is produced by the substances examined 

 (estimating this by the time of completion) varies in a remarkable, and, at first 

 sight, perplexing manner. In the case of the conia prepared by Dr Chmstison. 

 the former of these actions is the more powerful ; while in that prepared by Mr 

 Morson, and in methyl-conia, the two are nearly equally prominent. In a series 



