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MANUAL OF PHYSIOLOGY. 



different result followed when the current was sent through the 

 nerve in an upward direction (i. e., from the muscle), and when it 

 was sent in a downward direction (i. e., toward the muscle). The 

 stimulating .current is spoken of, in the former case, as an ascend- 

 ing current, and in the latter as a descending current. 

 The following is a tabular view of the law of contraction : 



To explain this law, the following points must be kept in view: 



1. In a breaking shock it is the disappearance of anelectrotonus 



which causes the stimulation. 



2. In a making shock it is the appearance of catelectrotonus 



which causes the stimulation. 



3. With the same current the make is more powerful than the 



break. 



4. Anelectrotonus causes reduction of irritability and conduc- 



tivity. 



5. Catelectrotonus causes increase of irritability. 



6. With ascending currents the part of the nerve next to the 



muscle is in a state of reduced functional activity (anelec- 

 trotonus). 



7. With descending currents the part of the nerve next the 



muscle is in a state of exalted activity (catelectrotonus). 



8. The reduction or exaltation of activity is much greater 



with strong currents. 



That only making shocks cause contraction with very weak 

 currents, simply depends on the greater efficacy of the entrance 

 of catelectrotonus into the nerve, which causes the making stimu- 

 lation. 



