Dr. Radcliffe on the Action of a Galvanic Current upon Nerve. 395 



On the side acted upon by the inverse primitive current, the por- 

 tion of nerve nearest to the muscles supplied by the nerve (the 

 muscles of the leg) is traversed, not by the inverse primitive cur- 

 rent, but by a direct derived current ; and hence we should expect 

 to find in the leg on this side (for at the time of these alternate 

 contractions the nerve is in the state in which the current produces 

 contraction alternately at the beginning of the direct current and at 

 the end of the inverse current) the effects of a direct current — con- 

 traction at the beginning of the current. We should expect to find 

 this ; for of two currents acting upon the same nerve, it is the one 

 nearest to the muscles supplied by the nerve which acts upon these 

 muscles. In the limb on the opposite side we should expect, on the 

 contrary, the effects of an inverse current — contraction at the end of 

 the current, for the lumbar nerves on this side are traversed by an 

 inverse derived current ; and this, as the Table shows, is actually 

 the case. 



A similar diagram and table will show that the results of passing a 

 direct primitive current through a portion of the lumbar nerves on 

 one side are in accordance with the same law. In this case, as in 

 the other, the acting current on both sides is the derived current. 

 On the side acted upon by the direct primitive current, the acting 

 derived current (acting because nearest to the muscles supplied by 

 the nerve) is inverse ; and therefore the limb on this side ought to 

 contract at the end of the current. On the opposite side, the course 

 of the derived current is direct, and therefore the limb on that side 

 ought to contract when the current begins to pass : and so it is. 



Fig. 2. 



The results of the action of a galvanic current upon a loop of 

 sciatic nerve are, after a time, analogous to those which have just 

 been mentioned. At first, the contraction attending upon the 

 beginning and ending of both currents affects the whole limb ; after 

 a time, the leg and thigh contract alternately, in an order which 

 changes with the direction of the current. 



21)2 



