384 Dr. C. B. RadclinVs Researches in Animal Electricity. [Apr. 8, 



the sheaths are affected without and within similarly by the natural and 

 artificial charges — in which the artificial may be added to the natural 

 charge, causing, not discharge, as in the case of the limb in which the cur- 

 rent is direct, but surcharge — in which, assuming the value of tension to be 

 10 for the artificial and 5 for the natural charge, and taking the figure used 

 before in illustration, the result of this combination of charges may be set 

 down thus : — 



Fig. 4. 



The case is one in which the artificial charge, by supplementing the 

 natural charge, may be supposed to retard the disappearance of the natural 

 charge, and with it the power of contracting ; for between this charge and 

 this power there is, without question, a connexion which may not be severed. 

 And if this be so, then it is not difficult to advance a step further and 

 perceive how it is that this artificial charge may restore the natural power 

 of contracting after it is lost, and how, in this way, after this power has 

 disappeared from the limb in which the current is direct, it may be brought 

 back again by reversing the position of the poles. In a word, it is not 

 altogether unintelligible that there should be along with the inverse cur- 

 rent an action which preserves and restores the power of contracting. 



And if the condition of the two limbs be thus different when the circuit 

 is closed, a clue is found, by tracing which it is possible to arrive at an 

 explanation of the different behaviour of the two limbs at the moment of 

 closing and opening the circuit. 



In the second period of the second stage (vide Table), the limb in 

 which the current is direct contracts at the moment of closing and not at 

 the moment of opening the circuit, and, contrariwise, the limb in which the 

 current is inverse contracts at the moment of opening the circuit and not 

 at the moment of closing it ; and most assuredly there is nothing anoma- 

 lous in these differences. 



In the limb in which the current is direct, as will appear on comparing 

 the two figures 2 & 3, there must be at the moment of closing the cir- 

 cuit a conflict between the natural and artificial charges of the fibres 

 before the stronger artificial charge can have the victory which it 

 gains in the end, — a conflict in which the neutralization of the natural 

 charge by an equivalent quantity of the artificial charge, must issue in 

 discharge ; and hence the presence of contraction at this moment, if con- 

 traction be coincident, not with charge, but with discharge. Indeed 

 there is a double reason for contraction at this moment ; for in addition to 



