The electrical constants of the ventral longitudinal muscle fibres of the stick insect Carausius morosus were determined by analysing the low-frequency cable properties of the fibre using short cable theory. At 20 °C in normal Ringer the membrane conductance (Gm) was 0.32 mmho.cm2, the sarcoplasmic conductivity (Gl) was 6.69 mmho/cm2 and the membrane capacity (Cm) was 12.2μF/cm2. In this solution the length constant (λ) was 2.13 mm and averaged 130% of the fibre length. Hypertonic (x 2) Ringers had no significant effect on Gi but increased the membrane conductance by about 35%. The effect of temperature on the electrical constants was also investigated: the temperature coefficient (Q10) of Gm was 1.44 and that of Gi was 1.41. The Q10 of the membrane capacity was 1.11.

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