LECT. XII. XIII. EFFECTS ON SCIATIC NERVES. 227 



to the periphery of the nerve (that is, in the direction of the 

 ramifications of the nerve.) At the moment when I close 

 the circuit, all the muscles of the thigh contract, the animal 

 utters loud cries, its back becomes forcibly bent, and its 

 ears are agitated. 



These phenomena recur when I change the respective 

 position of the electrodes ; that is, when I cause the current 

 to pass in the reverse way to that which it previously did, 

 and direct it from the periphery to the nervous centres. 



The effects which you observed at the moment when I 

 closed the circuit, are repeated when I open it, by inter- 

 rupting the communication of the conductors with the nerve, 

 both when the current is in the first direction (direct cur- 

 rent,) and when it is in the second, or opposite direction 

 (inverse current.) 



But during the time that the circuit is closed, whatever 

 may be the direction in which the current is passing, the 

 animal no longer presents any of these phenomena. We 

 shall soon see what kind of action ought to be attributed 

 to the latter during the time of its passage along the nerves. 

 If the current be applied to the nerves in such a way that 

 it passes across the nerve instead of along it, the contrac- 

 tions are more feeble ; and even entirely cease when the 

 experiment is conducted in such a manner that all the cur- 

 rent passes normally in the nerve. 



In repeating these experiments upon different rabbits we 

 foave remarked that, in general, the signs of pain evinced by 

 the animal are more violent at the commencement of the 

 passage of the inverse current, and that the contractions are 

 stronger and more obvious at the commencement of the 

 direct current. 



Whatever be the direction of the current in the nerves, 

 it gives rise, both at its commencement and at its inter- 

 ruption, to analogous phenomena ; but we constantly ob- 



