THE CORNEA is the most important refractive surface in the eyes of animals living in air. This often overlooked fact places the cornea second only to the retina in importance of the ocular tissues to visual function, for without this effect of the cornea no proper retinal image could be formed. In order for light to reach the retina, it is vital of course that the cornea remain transparent. Opacities of the cornea present a real problem in practical therapeutics and have led, therefore, to a consideration of why the cornea is transparent in the first place, what if anything can be done about opacities of the cornea and why the sclera is not transparent, since it is structurally homologous to the cornea.
In outlining an experimental approach to these questions, we have a number of well known observations to guide us. In the first place, it was pointed out