OF VITAL MOTION. 89 



cease on the breaking of the circuit; and hence the 

 contraction which takes place at the time may be the 

 natural consequence of this cessation. The slightness 

 of the phenomenon argues the operation of a more 

 partial agent than that which produced the more 

 violent contraction when the circuit was closed. The 

 short duration, also, favours the notion that it depends 

 upon some change in the nerves ; for when these cords 

 cease to convey any motive influence to the muscles, 

 we cease to have any contraction on the disruption of 

 the circuit when the current passes towards the foot. 



When, on the other hand, the influence of the pile 

 is transmitted through the limb in a contrary direc- 

 tion, namely, from the foot towards the thigh, and 

 when, therefore, the proper current of the limb coin- 

 cides with that of the pile, then the major contraction 

 follows the breaking and not the completing of the 

 circuit. Now, in this case, the electric tension must 

 have been increased during the continuance of the 

 current; for the limb forms a true additional element 

 of the pile, and yet the principal contraction does not 

 take place on the completion of the circuit, as we 

 might expect if this phenomenon was the consequence 

 of an impartation of the electric agent. Instead of 

 this, it supervenes when the circuit is broken, and 

 when there is a removal or partial neutralization of 

 force. Nor is it any objection that there is on closure 

 of the circuit the minor contraction, which disappears 



