Impedance spectroscopic experimentation at the superfused electrode vertical bar living tissue interface for human fetal skill was performed in three-electrode potentiostatic configuration for noble metal electrodes, with spectral analysis of the current. The impedance plane locus observed, reflects a diffusional element frequently in series with a distributed element of Havriliak-Negami type. In a minority of experiments no impedance could be defined. due to the presence of an additional peak in every cycle in the shoulder of the current waveform. This nonlinearity has never been reported before for a system of the present type. and may represent a novel pathological regime of anomalous diffusion. (c) 2006 Published by Elsevier B.V.