1869.] Dr. C. B. RadclifiVs Researches in Animal Electricity. 383 



opposite electricities apart — an assumption, be it remarked, which is not a 

 little borne out by the fact that the resistance which the voltaic current 

 encounters in the hind limbs of a frog when its course is up one limb and 

 down the other {vide fig. 1) is sufficient to keep the two limbs in opposite 

 electrical conditions as regards charge. In short, the natural electrical 

 condition of nerve and muscle during rest may be assumed to be one in 

 which the exterior of the sheath of the fibre is positive and the interior 

 negative — a state of charge which, taking 5 as the value of the tension, and 

 viewing the sheath in longitudinal section from within, may be figured thus : — 



Fig. 2. 



j- J 



The electrical condition of the fibres of the nerves and muscles of the 

 limb in which the current is direct may be assumed to be one in which the 

 exteriors of the sheaths are charged negatively from the negative pole, and 

 the interiors positively by induction — a state in which the disposition of 

 the two electricities forming the charge is the reverse of that which belongs 

 to the natural charge — in which, before this reversal can take place, there 

 must be a meeting of opposite electricities without and within the sheaths 

 which must result in the discharge of the weaker natural charge and of an 

 equivalent quantity of the artificial charge — which, assuming 10 as the 

 value of the tension, and taking the figure already used to illustrate the 

 state of things in the natural charge, may be represented thus : — 



Fig. 3. 



— ic 



The case, indeed, is one in which the artificial charge of the fibres involves 

 a reversal similar to that which happens naturally when these fibres, in 

 some instances at least, have lost a great portion of their activity, — in which 

 there may be supposed to be a similar reason, whatever that may be, for 

 failure in this activity : and hence it need not be altogether a matter of 

 wonder that the limb in which the current is direct should lose its power 

 of contracting more rapidly than the same limb when left to itself. 



The electrical condition of the fibres of the nerves and muscles of the 

 limb in which the current is inverse, on the other hand, may be taken as 

 one in which the exteriors of the sheaths are charged positively from the 

 positive pole, and the interiors negatively by induction — a state in which 



