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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 rhe'ophore 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 

 a piece of wet string or paper, by a strip of the animal's skin, by a 

 piece of wire, or by any other conductor, it matters not what, the 

 contractions occur alternately in the two legs just as they did before 

 the nerve was divided. Nay, it may be argued from the following 

 experiment, that reflex nervous action has nothing to do in producing 

 these alternations. Divide the lumbar nerves on one side, not where 

 they emerge from the spine, but where they pass into the thigh ; 

 raise the divided end of the nerve, and place it across the poles of 

 the galvanic apparatus. In this case the circuit of the derived cur- 

 rent is broken, and the action of this current is therefore put out of 

 the question. In this case, the nerve acted upon by the current is 

 still in connexion with the spinal cord, and through the cord and the 

 nerves proceeding from this cord, with the limb on the opposite side ; 

 and hence it might be supposed that the current might irritate the 

 cord, and so provoke contraction in the limb on the opposite side. 

 But the simple fact is, that the current may be passed inversely or 

 directly without producing contraction anywhere, except now and 

 then a few flickers in the muscular fibres in the lumbar region of the 

 side corresponding to that of the nerve operated upon. The simple 

 fact, indeed, appears to show that reflex nervous action can have 

 nothing to do with the contractions in the limb belonging to the 

 opposite side, which contractions are produced by the action of the 



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