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The lens weight of guinea pigs, rabbits and chickens is strongly correlated to the animals’ age, embryonic period included. Using the age values as logarithms, linear regressions can be estimated with a very good coefficient of determination, adapting themselves well to the empirical data. For practical uses a specified) table is available from which the statistically possible in)ference lens weight/age can be drawn.

The content of the free adenine nucleotides, of pyruvic acid, of citric acid and the oxygen consumption after inhibition with KCN were determined in bovine lenses and compared with normal values. Production of la Energy metabolism belled CO₂ was measured after addition of¹⁴C-6-glucose to the medium. The obtained data seem to confirm a 3 % participation of citric acid cycle in total glucose breakdown.

For investigations on age-dependent changes of lens metabolism, longitudinal studies are requisite. Graphic representation of such findings should be based on a proper arithmetic age scale. Using the lens weight for representing the age leads to distortion of the curves, whereby certain periods of life are liable to be overemphasized. In longitudinal studies, data on concentrations should never be given per unit weight, but rather for the whole lens. Absolute values of the whole, intact lens may be referred to a reference value, a percental representation of the curves is possible. With regard to the expectancy of life of test animals one may already state that longitudinal studies including the senile phase will only be feasible with rats.

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