The rate of potassium exchange of the lens.

When net accumulation of radioactive potassium by the lens is followed, it is found that at least 85 per cent of lens potassium is available for exchange. A method is presented for determining the rate of potassium exchange across the lens. Rat, rabbit, and calf lenses show rates of 22, 6, and 3 per cent per hour, respectively. While the exchange rate is clearly related to the size of the lens, the flux of potassium across the lens is nearly equal for rabbit and calf lenses. Rat lenses, however, have a potassium flux nearly double that of the other two species.