134 GENERAL PROPERTIES OF LIVING TISSUES 



over the nerve, and increase the intensity still 

 further. 



A strength will be reached at which closure 

 with the anode over the nerve will cause contrac- 

 tion, but the opening of the current will still be 

 without effect. A slightly greater intensity will 

 now bring out the anodal opening contraction. 1 



In the mean time the cathodal closing con- 

 traction has increased in force with each addition 

 to the intensity of the current. With about 18 

 cells, the muscle twitch on closure may give 

 place to a continued contraction or tetanus, the 

 cathodal closing tetanus. Further increase gives 

 cathodal opening contraction, and finally very 

 strong currents sometimes cause anodal closing 

 tetanus. Thus we have 



1. Cathodal closing contraction. 



2. Anodal closing contraction. 



3. Anodal opening contraction. 



4. Cathodal closing tetanus. 



5. Cathodal opening contraction. 



6. Anodal closing tetanus (rare). 

 Sometimes the anodal opening precedes the 



anodal closing contraction. 



1 Sometimes anodal opening contraction precedes the closing 

 contraction. This inconstancy results from variations in cur- 

 rent strength due to differences in the tissues surrounding the 

 nerve. 



