Dr. Radcliffe on the Action of a Galvanic Current upon Nerve. 393 



tion occurring at the end as well as at the beginning, of the cur- 

 rents, by applying alternately the feeble current of the forceps 

 and the stronger current of the chain. The author finds, also, that 

 the feeble current of the forceps will produce contraction at its end 

 as well as at its beginning, if the nerve be raised and placed as a 

 loop across the points of the forceps ; and not only so, but that the 

 same current will produce contraction only at its beginning, if it be 

 applied after slipping away the points of the forceps, and so allowing 

 the nerve to fall back upon the muscles. Hence the single con- 

 traction at the beginning of a feeble inverse or direct current, and 

 not at the end, instead of indicating, as Professor Bernard supposes, 

 the normal state of undisturbed and unexhausted irritability in the 

 nerve, must only be looked upon as the result of the action of a 

 feeble current under particular circumstances. In a word, the fact 

 is one which reflects the strength of the current rather than the 

 condition of the nerve. 



2. The curious alternating movements, which do not appear to 

 have been described hitherto, and which may be explained by means 

 of the key which Dr. Rousseau has put into our hands, are best 

 seen when the current is made to act upon the lumbar nerves of one 

 side, but they are also seen in the case where a loop of sciatic nerve 

 is acted upon. 



Take the back, loins, and hind limbs of a frog with the lumbar 

 nerves properly exposed, raise the nerves on one side into a loop 

 without dividing them, place them over the platinum poles of a 

 galvanic apparatus (a Pulvermacher's chain of ordinary length), and 

 pass the current. On doing this, as might be expected, there is in 

 the first instance, contraction in the limb to which the nerves acted 

 upon belong, but this contraction is slight and transient when com- 

 pared with the contraction which is set up in the opposite limb, the 

 nerves of which are not acted upon. In this opposite limb, indeed, 

 the contraction is sure to be both strong and tetanic. A little later 

 (and it is to the phenomena of this stage that the author wishes to 

 direct attention), and the results are as follows : — With the inverse 

 primitive current there is contraction in the leg belonging to the same 

 side when the current begins to pass, and contraction in the leg be- 

 longing to the opposite side when it ceases to pass ; with the direct 

 primitive current this order of contraction in the two legs is 

 reversed. 



In bringing about these curious alternations, the action of a 

 derived current is obviously concerned ; for on excluding this current 

 by means of Dr. Rousseau's rheophore bifurque, they come to an 

 end, and the movements resulting from the action of the current 

 are confined to the leg, the nerves of which are directly acted upon. 

 It is evident, also, that a derived current is what is wanting to pro- 

 duce the contraction in the limb belonging to the opposite side; for 

 after breaking the circuit of the derived current by dividing the 

 lumbar nerves where they emerge from the spine, and separating the 

 divided ends, and after then completing the circuit by dropping 

 down the end of the divided nerve, or by bridging over the gap by 

 Phil. Mag. S. 4. Vol. 20. No. 134. Nov. 1860. 2 D 



