Abstract
1. Twitch fibres were isolated from the semitendinosus muscles of frogs. The sarcolemma was made more permeable by a 30 min soak in a solution containing 47·3% glycerine (v/v), 2 mM-EGTA and 10 mM phosphate buffer, pH 7. This was followed by a 30-60 min soak in a solution containing the non-ionic detergent Lubrol-WX. The fibres were then placed in a relaxing medium containing (in mM): KCl, 100; MgCl2, 1; ATP, 4; EGTA, 2; imidazole buffer, 10; pH 7·0.