130 



PHYSIOLOGY OF MrsfLER AXU NERVES. 



indicate the change \\hich the excitabilit y undergoes at 

 any definite p >int in the nerve, let us suppose a straight 

 line drawn at this point at ri^ht angles to the longitn- 

 dinal direction ,>f the n-r\e. and let this line he made 

 longer in prop .rtioii as the change i> greater. In order. 

 inoreo\er, to show that the changes which occur toward 

 the anode are of an opposite tendency to those toward 

 the kathode, let the line on the anode side be drawn 

 downward, that on the kathode upward. ]'>y connect ing 

 together the heads of these lines a curve is obtained 

 which diagrammatical]? represents the changes at each 



rr 



X 



X 



ixrs rxni-:u TIIK IXFI.IKM i. OF 

 VAKVIM. yn:i:.\<:Tii. 



])oint. Of the three CUrVCS, the middle represents the 

 condition under the influence of a current of medium 

 strength; (he other (wo curves, indicated, the one by 

 short lines, the other by a dotted line, represent ihe 

 conditions under the influence of a >trong and of a 

 weak current respectively. These curves show thai tin 

 changes are more marked in proportion as the cur- 

 rent is stronger ; that they are most strongly developed 

 exactly at the electrode poinl>; and, finally, that the 

 neutral point, under the influence of currents of dif- 

 ferent degrees of strength, assumes a \ariable portion 



betWeell th'- electrodes. 



