382 Dr. C. B. RadclifiVs Researches in Animal Electricity . [Apr. 8, 



the experiment. The case, indeed, appears to be not remotely analogous 

 to that in which the prepared limbs of a frog are made to hang from the 

 prime conductor of an electrical machine, and then charged and discharged 

 alternately ; for here the rule as to contraction is the same, namely this, — 

 that the limbs contract, not when they receive or while they retain the 

 charge, but at the moment of discharge. 



That the changes of tension in question do actually affect the limbs as 

 they are found to be affected under the action of the inverse and direct 

 current appears to gain in probability as the matter is more fully inquired 

 into. 



There is no difficulty in referring to changes of tension the phenomena 

 belonging to the first stage (vide Table). If the closing and opening of the 

 circuit be attended by discharge, and if contraction be coincident, not with 

 charge but with discharge, the presence of contraction in both limbs at the 

 moments of opening and closing the circuit is in accordance with rule ; and 

 if the discharge at the opening of the circuit be weaker than that which 

 happens at the closing, it is easy to see that with a weak battery the 

 stronger discharge at the moment of closing the circuit may be strong 

 enough to tell upon the muscles when the weaker discharge at the opening 

 of the circuit is not strong enough to do so. Indeed it is plain that the ab- 

 sence of contraction at the opening of the circuit in the case where a weak 

 battery is used is merely a matter of wanting battery power, for the missing 

 contraction is made to appear by simply supplying this want. 



Nor is there any difficulty in applying the same key to the explanation 

 of the phenomena belonging to the second stage (vide Table). 



It is a fact that the power of contracting is affected very differently in 

 the two limbs by the action of the electricity. The limb in which the 

 current is direct loses this power much more speedily than it does when 

 left to itself ; the limb in which the current is inverse retains this power 

 much longer than it does when left to itself ; the limb in which a direct 

 current has been passed until the power of contracting is at an end re- 

 covers this power, and this, too, more than once, if the direction of the 

 current be changed for a time. Of these facts — the impairment of the 

 power of contracting in the limb in which the current is direct, the pre- 

 servation and restoration of this power in the limb in which the current is 

 inverse — there can be no question. 



There is also reason to believe that there are electrical differences in the 

 two limbs which will, in some degree at least, account for the differences 

 in the power of contracting, and for other differences which have yet to be 

 considered. 



The conclusion already arrived at respecting the natural electricity of 

 nerve and muscle is that the state during rest is one of charge — that, ordi- 

 narily at least, the sheaths of the fibres are charged positively at their 

 exterior and negatively at their interior. The resistance of the animal 

 tissues to electrical conducion, it is assumed, is sufficient to keep the two 



