120 GENERAL PROPERTIES OF LIVING TISSUES 



tonus). In the intrapolar region, the cathodal 

 touches the anodal area at the so-called indifferent 

 point. This point approaches the cathode when 

 the intensity of the polarizing current is increased. 



The greater the length of nerve between the 

 electrodes, the greater the extrapolar electrotonus. 

 Catelectrotonus rises rapidly to a maximum as 

 soon as the circuit is closed, and then gradually 

 wanes. Anelectrotonus develops more slowly and 

 does not reach its maximum for some time after 

 closure. 



On the opening of the circuit, the conditions at 

 the anode and cathode are reversed, the irritability 

 falls at the cathode and rises at the anode. The 

 fall in the cathodal region is of short duration, 

 and the irritability soon returns again towards 

 normal. In the anodal region, the rise on open- 

 ing is unbroken. 



Changes in Conductivity. We have seen 

 that the irritability is altered by the galvanic 

 current. The conductivity also is altered. 



Connect a dry cell through a pole-changer with 

 cross-wires to a pair of non-polarizable electrodes 

 placed in the holders o,f the moist chamber 

 farthest from the muscle (Fig. 32). Leave one 

 wire uncoupled until the current is wanted. 

 Connect another cell with the primary coil of 

 the iiiductorium arranged for break induction 



