394 



Royal Society : — 



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 

 galvanic current on one set of lumbar nerves ; and, certainly, with 

 the key furnished by Dr. Rousseau, reflex nervous action is not 

 required to explain the phenomenon. 



The following diagram will give the case in which the lumbar 

 nerves on one side are acted upon by the inverse primitive current, 

 a a being the lumbar nerves, P N the poles of the galvanic appa- 

 ratus, the black arrow the primitive current, the dotted arrows the 

 derived current. The results, as seen in contraction in the limb 

 belonging to the same side, or in that belonging to the opposite side, 

 are seen in the Table below the figure. The case is plain. 



Fig. 1. 



