RELATIVELY little is known about the anabolic processes (synthesis) of various components of the lens, although many studies have been made on the breakdown of metabolites and a few on the net degradation of some of its structural elements. Studies on metabolism of the lens have been limited almost exclusively to catabolic reactions. To the authors' knowledge, this is the first quantitative study of synthesis of any lens component. The significance of synthetic processes in normal tissue physiology has been established in recent years by Schoenheimer and associates.1 By means of molecules labeled with different isotopes, these workers studied various separate and coupled chemical reactions occurring within tissues and evolved a new concept of "the dynamic state of body constituents." In a book by this title,1Schoenheimer pointed out that "all constituents of living matter whether functional or structural, of simple or complex constitution, are in a steady state