ANATOMY AND PHYSIOLOGY OF NERVOUS SYSTEM. % 609 



the nerve, that is, kathode. Practically, a kathode and anode exist 

 ibout each pole in the tissues. 



If, on the contrary, the electrode under observation is the 

 kathode, the current enters the nerve by a series of points which 

 collectively constitute a peripolar region and it leaves the nerve by 

 a series of points which collectively constitute a polar region. The 

 current at its entrance into the body diffuses widely, and at its exit 

 it concentrates ; its density is greater close to the electrode, and the 

 greater the distance of any point from the electrodes the less the 

 current density at that point. Hence it is obvious that current den- 

 sity is greater in the polar than in the peripolar region. Waller 

 makes the formula for man as follows : 



Weak current K. C. C 



Medium current K. C. C. A C. C. A. O. C 



Strong current K. C. C. A. C. C. A. O. C. K. O. C. 



K. C. C. = Kathodic closure contraction. 



A. C. C. = Anodic closure contraction. 



A. 0. C. = Anodic opening contraction. 



K. 0. C. = Kathodic opening contraction. 



Making "yes" for contraction and "no" for rest we have : 



KATHODE. ANODE. 



MAKE. BREAK. MAKE. BREAK. 



Weak current Yes No No No 



Medium current Yes No Yes Yes 



Strong current Yes Yes Yes Yes 



Reaction of degeneration denotes the reaction of diseased nerve 

 and muscle on man. As regards the nerve, the reaction of degen- 

 eration consists in the abolition of excitability to the induced cur- 

 rent, while the excitability to the constant current is exaggerated; 

 the muscular contraction is also greatly prolonged and galvano-tonus 

 (tonic contraction) is easily produced. The normal contraction 

 formula just given is departed from, the most characteristic feature 

 of this departure being a reversal of the normal order of appear- 

 ance of K. C. C. and A. C. C. Normally, K. C. C. appears with a 

 weaker current than A. C. C. In a well-marked reaction of degen- 

 eration A. C. C. appears with a weaker current than K. C. C. There 

 is no satisfactory explanation of this reversal (Waller). 



The musical symbols < > (crescendo and diminuendo) indicate 

 increase and decrease. They are used in electrical formula to show 

 the relationship of one reaction of muscle becoming greater than 

 another. Thus: A. C. C. > K. C. C. = the anodic closure contrac- 



