It has always been assumed, without actual evidence, that the various lenticular proteins were homogeneous in chemical composition. However, investigations on many other proteins have indicated that most proteins are heterogeneous in nature. On this basis, it is to be expected that the lenticular proteins are also composite. Technical difficulties prevent the fractionation of most of the naturally occurring proteins, but fortunately the nature of the anatomic growth of the lens aids in the isolation of the lenticular proteins, which are presumably of various ages. Since there is no reason to believe that the lenticular proteins of older cellular fibers are renewed during the life of the lens, the comparative quantitative analysis of the isolated proteins of the lamellae of the lens should give an insight into the process of growth of the lens. The chronological changes in the lens protein also have a bearing on the etiology