ELECTROTOXUS. 



127 



conducted ; by means of proper apparatus the current 

 may be strengthened or weakened, and may be closed 

 and interrupted by means of a key at s. Let a current 

 from a sliding inductive apparatus pass through another 

 portion of the nerve, e.g. a 6, and let us find that posi- 

 tion of the secondary coil at which the muscle exhibits 

 marked pulsations of medium strength. The changes 

 which occur in these pulsations when the current in 

 the portion c d is alternately closed and interrupted 



ft-' 



Fig. 30. Electrotoxus. 



must now be observed. It is found that theee changes 

 depend on the direction of the current within the nerve. 

 If the current passes in the direction from c to d, then 

 the action of the same irritant is weakened in the por- 

 tion a 6 as soon as the current is closed, but reo-ains its 

 former strength as soon as the current is interrupted. 

 In this case, therefore, the excitability in the contiguous 

 portion a h was lowered or hindered by the influence 

 of the constant current traversing the portion c d. If, 

 however, the constant current is reversed, so that it 



