Top Panel: Ratio of 57Fe/56Fe concentration in plasma samples obtained from the PV of P1, P2, and P3, and the CAV of P4 at different times after 57Fe injection into the stomach. Traces: red, P1; purple, P2; green P3; blue P4; dashed black line is the ratio of natural abundance of 57Fe/56Fe. Error bars are standard deviations. Bottom Panel: Plot of 57Fe concentration of PV plasma vs. time after injecting 57FeII into the stomachs of P1 (red), P2 (black), and P3 (green). Solid lines are simulations obtained using equation [1] and the parameters in Table 2. The intensity of the P1 plot was reduced 2-fold (×0.5).