The lens, being devoid of blood vessels in postnatal life, is dependent on its surrounding media for nutrition and respiration. However, because of its internal oxidative mechanism, it is partly independent of the aqueous for its respiration. It is fortunate that this is so, for, according to Duke-Elder,1the oxygen tension of the aqueous is insufficient to meet the requirements of the lens. The internal oxidative system of the lens functions through the agencies of glutathione and vitamin C, or cevitamic acid. The latter is present in the aqueous and lens, while the former is found only in the lens. These substances are capable of being reversibly oxidized and reduced, thus forming a so-called "redox" system. This property depends on the ability of glutathione and vitamin C to accept hydrogen, and in this process the hydrogen donor (the lens) is oxidized. That the reversibly oxidized vitamin C is