1870.] 



Dr. C. B. Radcliffe on Animal Electricity, 



25 



wire at the positive pole the contractions continue no longer than 1 5' or 

 20' in the case where the current is direct, and in that in which the cur- 

 rent is inverse also. With the earth-wire at either pole — that is to say, 

 the part acted upon by the inverse current and the part acted upon by the 

 direct current are both made to contract for the same length of time, the 

 contraction in both parts being 60' or longer if the wire be at the negative 

 pole, and for no longer than 15' or 20' if it be at the positive pole. Now 

 the earth-wire changes the charge of free electricity associated with the 

 inverse and direct currents, but it does not alter the course of those cur- 

 rents. When the voltaic circuit is insulated, the part acted upon by the 

 inverse current is charged positively, and that acted upon by direct current 

 negatively, the charge in each case proceeding from the voltaic pole which 

 happens to be nearest ; when the earth-wire is put to either pole, the free 

 electricity of that particular pole runs off to earth, and the parts between 

 the poles (the half traversed by the inverse current and the half traversed 

 by the direct current alike) are charged with the free electricity of the 

 other pole, — with positive electricity if the wire be at the negative pole, 

 with negative electricity if it be at the positive pole. The whole case, 

 indeed, is one which seems to admit of only one conclusion, namely this — 

 that the longer or shorter continuance of the contraction must have its ex- 

 planation, not in the current being inverse in the one case and direct in the 

 other, but in the free electricity associated with one or both these currents 

 being positive in the one case and negative in the other, the contraction 

 continuing for the longer time when this electricity is positive, and for the 

 shorter time when it is negative. And that this should be so is not alto- 

 gether unintelligible if the natural electrical condition of the fibres of living 

 nerve and muscle be what it has been assumed to be — a condition in which 

 the outsides and insides of the sheaths are in opposite electrical states, the 

 charge on the outside, usually positive, inducing the opposite charge on the 

 inside ; for on this assumption it may well be that a positive artificial 

 charge to the outsides of the sheaths may preserve the natural activity of 

 the fibres, and so favour the continuance of the contraction by keeping up 

 their natural charge, the positive electricity outside the sheaths inducing 

 negative electricity inside the sheaths ; and that a negative artificial charge 

 may have the contrary effect, the negative charge outside the sheaths in- 

 ducing positive electricity within the sheaths, and so producing that re- 

 versal in the relative position of the two electricities which is only met 

 with when the fibres are upon the point of losing their activity. 



Voltaic electricity, therefore, would seem to act upon nerve and muscle, 

 not by the constant current which passes while the circuit is closed, but by 

 the charge of free electricity, positive or negative, associated with this 

 current, and by the extra-currents which pass at the moments of closing 

 and opening the circuit, which extra-currents are in very deed discharges, 

 the charge being favourable to the continuance of activity when positive, 

 and unfavourable when negative, the instantaneous currents or discharges 



