154 ON NERVE-EXCITATION BY THE NERVE-CURRENT. 



these contractions 'paradoxical.' He observed contraction of the 

 muscles supplied by the peroneal nerve when the tibial nerve was 

 excited, and vice versa, and with excitation of the sciatic below the 

 origin of its femoral branches he saw contraction of the muscles sup- 

 plied by these nerves. He showed that the contractions in question 

 are caused by electro tonic currents which pass from excited to 

 adjacent fibres. And in point of fact the conditions of his experi- 

 ments were such that there can be no doubt concerning the correct- 

 ness of this explanation. For he sent the whole current of a 

 Grove's cell through the nerve by means of platinum electrodes, 

 and observed that the paradoxical contraction appeared with greater 

 certainty and strength as the electrodes were brought closer to the 

 point where the indirectly excited nerve branched off. According 

 to a figure which he gives of the arrangement of an experiment, the 

 point where the nerve branches and the nearest electrode are distant 

 from each other by not more than about 7 mm. 



I have experimented under quite different conditions. In using 

 the battery-current, for instance, the weak currents which are 

 obtained with one Daniell and only I to 2 mm. of the du Bois- 

 Reymond rheochord consisting in a double wire of platinum, were 

 sufficient. The platinum electrodes were distant from each other 

 about 2 mm., and between the femoral branches the muscles of 

 which were excited to secondary action and the nearest electrode, 

 there was a length of nerve of at least 30 mm. If I used un- 

 polarisable electrodes, no more than 25 mm. of the rheochord 

 wire were required to give the same result. With induction 

 currents, using only i Dan., it was often sufficient to place the 

 secondary coil at a distance of 50 cm. in order to obtain strong 

 secondary effects in the thigh when the sciatic nerve was tetanised 

 at the knee. I have also repeatedly divided the femoral branches, 

 BO that none remained attached to the sciatic nerve between the 

 electrodes and the origin of the crural nerve from the plexus 40 to 

 42 mm. higher up. Under these circumstances the muscles 

 supplied by the crural nerve were excited to strong secondary 

 tetanus when I tetanised the sciatic at the knee with the coil 

 standing at a distance of about 40 cm. Whereas du Bois- 

 Reymond obtained stronger secondary effects the nearer he moved 

 the electrodes to the branch, I obtained progressively weaker 

 effects which soon disappeared, if I moved the electrodes further 

 from the section, i.e. nearer to the branches that were to be 

 secondarily excited, especially with ascending (abterminal) currents. 



