Abstract
The tetanus curve and fatigue of sartorius muscle of the frog were investigated.
Muscle was mounted in the fluid bath and stimulated in various electric fields by alternative or successive square pulse current.
1) In Ringer's solution the successive stimulation of 20-25c/sec was so less effective for contraction conpared with the alternative stimulation. In any other frequencies, howerver, both stimulations produced nearly the same effects.
2) Delicate coupling-process should be in between membrane depolarization and contraction, because even the alternative stimulation could not exhaust the muscle force completely.
3) When the concentration of potassium in Ringer's solution was raised up to 5-9mM, subsituted for sodium, the threshold for electric stimulus decreased, but contracting force remained, unchanged.
4) When the action potential was abolished by excess potassium (14mM), 0.06% procaine or sodium free solution (cholin chlioride solution), the muscle still could be stimulated to contraction by electric current, and the alternative stimulation was more effective than the successive one.
