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galvanism, so as to excite much more the muscles of the left side 

 united with the spinal cord, than those of the right side. 



The muscles of the left side were excited : 



1st. Directly by the galvanic current. 



2d. In consequence of the excitation of the motor nerves. 



3d. In consequence of the excitation of the spinal cord, directly 

 by the galvanic current, and secondarily in consequence of the 

 excitation of the sensitive nerves. 



So that the muscles on that side were moved not only by the 

 direct excitation on them, but also by a reflex action, and in conse- 

 quence of the direct excitation of the spinal cord. 



As to the muscles of the right side, they were only excited by 

 the small part of the galvanic current passing in them. During the 

 first, and perhaps the second and the third week after the section of 

 the ischiatic nerve, the muscles were also slightly excited by the 

 motor fibres of that nerve, but after that time these fibres had lost 

 their vital property, and were unable to excite a contraction in 

 muscles. 



From this analysis it results clearly that the mode of comparison 

 of the two limbs, by the passage of a galvanic current, as it has 

 been employed by Marshall Hall, could not decide in which side 

 the muscles were more irritable. 



The use of strychnine, also, could decide nothing in this ques- 

 tion, because, as I have proved in a former article, this poison is not 

 able to act upon muscles. It acts only on the nervous centres, and 

 especially on the spinal cord. Therefore, the production of tetanus 

 in one limb and not in the other, in the experiment of Marshall 

 Hall, proves nothing at all as to the degree of muscular irritability. 



To know what is that degree, it is necessary to separate the two 

 limbs from the trunk, and then to excite directly the muscles. Mar- 

 shall Hall has made this experiment, but he says nothing about the 

 circumstances under which it was performed, and these circum- 

 stances were, as it will be shown, extremely important. 



In my experiments, instead of dividing only the ischiatic nerve, 

 I divided the four nerves going to one of the posterior limbs, of 

 many frogs, in whom the spinal cord was divided immediately 

 behind the roots of the brachial nerves. 



I have found on the separated limbs of these frogs : 



