|MadSci Network: Biochemistry|
The lens of the eye consist of a surrounding acellular membrane called the capsule, and two types of cells: epithelial cells and fiber cells. The epithelial cells cover the front and lateral surfaces of the lens, and divide at the equator (edge of the lens to give rise to the oriented fiber cells, which comprise the bulk of the lens. The fiber cells are characterized by a very high content of the protein crystallin (about 1/3 of the weight of the lens). This crystallin protein is probably what was refered to as "crystalline substances". In fact it is not crystalline. The remainder of the weight of the lens is made up of water and various small organic compounds. The crystallin is actually a mixture of four proteins, alpha-, beta-, gamma-, and delta crystallin. Mammals have the first three in their lens, with the delta found only in reptiles and birds. As far as the refractive index of the lens, you have me - I have not come up with a good reference. Should you be interested in more on the biochemistry of the lens or of the eye in general two useful references are: The Eye, edited by Hugh Davson (1984), Academic Press. Biochemistry of the Eye, by Elaine R. Berman (1991) Plenum Press Hope this answers your first question!
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