1869.] Dr. C. B. RadchfiVs Researches in Animal Electricity. 381 



case is one in which, supposing the value of the tension at each of the poles 

 to be 10, the state as to tension at different points between the poles is 

 found to be that which is indicated by the figures in the accompanying 

 sketch : — 



Fig. 1. 



o 



This, then, being the state of the limbs as to tension under these circum- 

 stances, it is plain that there must be definite changes in tension at the 

 closing and opening of the circuit. It is plain that the limbs must be tra- 

 versed by a discharge at the moment of closing the circuit ; for the charge 

 of the poles must diminish in direct proportion to the freedom with which 

 the current passes. It is plain also that the opposite electricities which 

 are accumulated in the limbs while the circuit is closed must be discharged 

 when the circuit is opened. It is possible also that the discharge at the 

 opening of the circuit may be less in amount than that which occurs at the 

 closing of the circuit ; for immediately after the opening both the limbs may 

 be supposed to receive a charge from the pole with which they happen to 

 remain in connexion, which charge will to some degree counteract the dis- 

 charge. 



How then 1 Is it possible that these changes of tension may have to do 

 with the motor phenomena which are ascribed to the action of the direct 

 and inverse currents ? 



That, the changes of tension in question are of themselves sufficient to 

 tell upon the muscles in the requisite manner is proved by a new and very 

 curious experiment. The two hind legs of a frog, prepared and arranged 

 as in the experiment for exhibiting the action of the inverse and direct 

 currents, are connected, time after time, first with one pole of the battery 

 and then with the other, but never with the two poles at once. The result, 

 for a time at least, is contraction in one or both of the limbs when they are 

 thus carried from one pole to the other. There is a succession of charges 

 and discharges ; for before a charge can be received from either pole this 

 charge must neutralize the charge carried away from the other pole. The 

 contraction must have to do with changes of tension, and with changes of 

 tension only ; for the circuit remains open from the beginning to the end of 



