50 PRACTICAL PHYSIOLOGY 



wire. Finally, the effect of a strong current is to be 

 studied by eliminating the rheochord altogether, 

 and, if necessary, adding more cells to the battery. 

 If the nerve be very excitable 1 the muscle may 

 remain in contraction during the whole time of the 

 passage of a strong descending current (closing 

 tetanus), and may also remain contracted for a con- 

 siderable time after the removal of a strong ascend- 



Glass rod. 



-Curarized sartorius. 



FIG. 33. POLAR EFFECTS OF CONSTANT CURRENT UPON MUSCLE. 



ing current (Ritters opening tetanus). If Ritter's 

 tetanus is obtained the nerve may be cut between 

 the electrodes. The tetanus instantly ceases be- 

 cause the point where the stimulus occurs (the 

 original anode) is cut off. 



That in closing a constant current the excitation 



1 The excitability of a muscle-nerve preparation is greatest when 

 made from a frog which has been kept in a cold place or in contact 

 with ice, and then for half an hour at the ordinary room-temperature 

 pithed. 



