IN a study of the organization of the cerebral cortex, alternative experiments on the evoked potentials of the hippocampus and of the isocortex were performed in order to apply the findings in the more simply constructed layer of Ammons pyramids to resolution of the electrical fields of the cortex proper. The former consists essentially of one layer of similarly oriented cells, whereas the latter structure shows duplication in the form of stratified supragranular and infragranular layers. We have found that the electrical correlates of the layered isocortex are not in the direction that at first seemed obvious. For one thing, the d.c. standing potential across the unstimulated isocortex is less rather than greater than that across the pyramid cell-layer of the hippocampus, suggesting that the cell dipoles are not arranged in series. Furthermore, the overall potentials of activation of an area of the isocortex show an increase in magnitude during inactivation of the supragranular layer.