Swelling of the cornea in vivo after the destruction of its limiting layers.

]T is well known that the cornea will swell if excised and placed in an aqueous solution, and the attention of many investigators has been turned to the reason for its unswollen state in the normal eye. It is generally accepted that the explanation lies in the properties of the limiting membranes of the cornea and various theories have been propounded as to the mechanism of their action. Leber (1873) based his explanation on the high degree of impermeability to aqueous humour shown by him to be possessed by the endothelium, and Cogan and Kinsey (1942), finding that water could pass freely across both limiting membranes of the cornea and that they were semipermeable, accounted for the deturgesced state of the normal stroma by the removal of water from it by hypertonic tears and aqueous humour. Davson (1949a), and Maurice (1951) considered that this explanation was improbable and concluded that some active extrusion must occur at the membranes. In the light of this hypothesis it would be interesting to investigate the effect of metabolic poisons on the degree of corneal hydration, as this could be an indication of the processes involved in the removal of water from this tissue. In order to assess the degree of impairment of the function of the limiting membranes, it was decided to find out as a preliminary step what was the potential swelling that could occur in vivo if this function was completely abolished by their mechanical removal. At the same time techniques for measuring the swelling could be developed which would be available for the subsequent experiments with poisons. The only quantitative investigations of corneal swelling after removal of the epithelium or endothelium, of which we are aware, are those of Kinsey and Cogan (1942), which were restricted to the excised tissues. As far as removal of these membranes in vivo is concerned, Leber (1873) noticed a considerable increase in thickness after removal of the endothelium. There do not, however, appear to be any corresponding observations for the epithelium in the