In studying the crystalline lens system, we are confronted by conditions entirely different from those regulating any other organisms of the entire body. Here we find a living structure, the lens, undergoing all the successive changes of development, progression and retrogression, devoid of the usual complicating factors— blood-vessels, nerves and lymphatics—subject to the influence of its nutritive supply, which is brought to it by the vitreous, possibly by the aqueous, both of which are likewise devoid of these complicating factors—bloodvessels, nerves and lymphatics. The lens is also subject to the mechanical influence exerted on its shape by the zonula Zinii. To this latter influence, the lens responds in a purely passive manner, due to the inherent elasticity of its fibers. Subsequent to its embryonal development period of growth, the lens consists of closely packed lamellæ of fibers, which become more densely packed as we approach the center, thus forming the