PRACTICAL PHYSIOLOGY 51 



occurs at the kathode, in opening at the anode, can 

 be shown upon a curarized sartorius laid upon a 

 pair of non-polarisable electrodes (Fig. 33). It 

 will be observed that the twitch begins at the 

 kathode when the current is closed ; indeed, the 

 muscle may remain more or less contracted at that 

 end during the whole time of the passage of the 

 current. On the other hand, on opening the cir- 

 cuit the twitch begins near the anode, and may again 

 be followed by a prolonged contraction. These 

 prolonged contractions correspond to the closing 



FIG. 34. EFFECT OF A CONSTANT CURRENT ON NERVE CONDUCTION. 



and opening tetanus obtained through a motor 

 nerve. They show that excitation is produced not 

 only at the make and break but also during the 

 passage and for a short time after the cessation of 

 a strong constant current. 



Effect of a constant current on conduction in 

 nerve. Place the spinal ends of the two sciatic 

 nerves of a frog upon a single pair of stimulating 

 electrodes, and on one of the nerves between the 

 point to be stimulated and the muscle place a pair 

 of non-polarisable electrodes connected through a 



