ANATOMY AND PHYSIOLOGY OF NERVOUS SYSTEM. 



667 



bility from below normal to normal, or above, at the break of the 

 current at the anode, acts as stimuli to the muscular contraction. The 

 constant current, independent of the changes in excitability, lowers 

 the conductivity of the nerve. With the exception of the weakest 

 current, the conductivity at the kathode and the anode is diminished, 

 and with currents moderately strong the conductivity is blocked. 



Fig. 269. Pfliiger's Law of Contraction or Nerve-muscle Preparation. 

 Des, Descending current. Asc, Ascending current. 



'he conductivity at the anode is but little affected and is much 

 higher than at the kathode, so that at the time of full kathodic block 

 the nerve-impulse still freely travels through the region around the 

 positive pole. With stronger currents, conductivity at the anode 

 diminishes so much in the intrapolar region that it blocks the nerve- 

 impulse, but this is to be looked upon as a stretching of the diminu- 

 tion of conductivity which has crept along the intrapolar area from 

 the kathode. 



