Frequency dependence of the frog skin impedance

At frequencies between 20 Hz and 1 kHz the impedance locus of the isolated frog skin is circular; below 20 Hz the resistive component of the impedance is frequently greater than would be expected from extrapolation of the high-frequency locus. At frequencies greater than twice the highest frequency at which there are deviations from the circular locus the variation of impedance Z with angular frequency omega is closely described by the equation Z equals r1 plus r o/[1 plus (j omega tau)1-alpha], where j is square root--1, r 1 and r 0 are resistances, tau is a time constant and alpha a constant in the range 0.02-0.14.