Distribution of radioactive iron over body compartments in mice raised on diets different in iron content. Measured values are given as mean with standard deviation. The best fit obtained by parameter estimation is drawn as continuous curve. All data were normalized to initial dose of radioactive tracer (100%), with allowance made for a slow total excretion (see methods). The kinetics of plasma clearance is very rapid (characteristic time about 60 to 100 min) and therefore not visible in detail on the scale applied here.