Histological study of the spongy state reveals that discontinuous segements of myelinated axons severed by the formation of the sponge cavities often appear morphologically intact. Since fibers severed from their cell bodies degenerate rapidly, it is concluded that the process occurs agonally or postmortem. The resemblance between the sponge cavities and postmortem gas cysts is emphasized, as are the differences between the spongy state and the liquid accumulation in cerebral edema. The presence of histochemically demonstrable glycogen in the brain in association with the spongy state, at times in specific relation to the spongy areas and even to individual sponge cavities, is described. It is suggested that glycogen reservoirs serve as substrate for the rapid evolution of gaseous carbon dioxide following the cessation of blood flow, and that this gas forms the sponge cavities. The glycogen accumulation and the decarboxylating capacity may be part of each of the heterogenous disease processes with which the spongy state is associated, and pathological changes of greater significance than the sponginess, characterize each of these varied disease states. Other forms of the spongy state may exist.