THE PHYSIOLOGY OF THE NERVE-FIBRE 



583 



Ascending. 



Make. Break. 



O. C. 



Descending. 



Make. Break. 



C. O. 



This regular order of contractions for currents of different intensities is known as 

 " Pfliiger's law of contractions." 



The altered conditions at the anode and at the kathode can be 

 proved by stimulation in these regions by single induction shocks, using 

 ordinary electrodes. Fig. 324 shows the result of such an experiment. 



EIG. 324. SHOWING EFFECT OF STIMULATION IN REGIONS OF KATHODE AND ANODE. 



The above alterations of excitability are sometimes referred to as 

 " electrotonus "; they are better described as i; electrotonic alterations 

 of excitability." The term " electrotonus " is best employed for the 

 electrical currents which occur in the nerve itself in the parts outside 

 that through which the constant current passes. The current which 



\VSatelectrotoriuW 

 Current. 



FIG. 325. SHOWING DIRECTION OF AN ELECTROTONIC AND KATELECTROTONIC 



CURRENTS. 



is found in the neighbourhood of the anode is termed the anelectrotonic 

 current, that in neighbourhood of the kathode the katelectrotoiiic. 

 Galvanonietric observations show that the anelectrotonic current 

 flows towards, and the katelectrotonic current away from, the polarized 

 region* (Fig 325 ) 



