COGAN1 has done much to clarify knowledge of the circulation of fluid from the limbus through the stroma. The schematic drawing (fig. 1) illustrates his theory of fluid movement through the cornea. Figure 2 indicates his inability to produce bullous keratitis by forcing fluid into the cornea from the aqueous. He was able to produce typical bullous keratitis only by the absorption of fluid from the outside through the hypertonicity of the cornea, the symbols −, + or +, + + representing the artificially produced osmotic relations. He found (fig. 3) that the epithelium and endothelium are impermeable to sodium chloride and thus act as a semipermeable membrane, and that the stroma is permeable to sodium chloride and consequently is unable to act as a semipermeable membrane. Water thus remains, to produce bullous keratitis, because there is no further osmotic pressure to transfer the water through the stroma. His experiments showed that electrolytes,