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MANUAL OF PHYSIOLOGY. 



It was found that, with the same strength of stimulation, not 

 only were different degrees of contraction produced with making 

 and breaking shocks, but also that, other things being similar, a 

 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., towards the muscle). The 

 stimulating current is spoken of, in the former case, as an ascending 

 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- 

 trotouus). 



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. 



