Fig. 2. Typical recordings of twitch and tetanic forces developed by direct or indirect stimulation at three different temperatures, 4°C, 12°C and 22°C. Twitch and tetanic forces at the different temperatures were recorded from the same preparations. The duration of the stimulation in tetanus was 1 s. Forces obtained by indirect stimulation (thick lines) are expressed relative values to those obtained by direct stimulation (thin lines) at each temperature. Temperatures and stimulation frequencies in tetanus are denoted for each recording.