In a simulated vessel model study, the ratio Vmean / Vmax was decided to be 0.55 changing the hematocrit of the blood, the diameter of vessels, and the velocity of the flow. (Vmean is a mean velocity and Vmax is a maximum velocity of the portal blood flow). The fasting value of the portal blood flow (PVF) in normal controls using a linear-type B mode electroscanner and pulsed Doppler flowmeter was 720±351 ml/min (0% increase) (Actual value (% change)). Forty minutes after an oral ingestion of 300 ml of 25% glucose solution, PVF came up to the peak value of 1,416±513 ml/min (101±72% increase). PVF in gastrectomized patients after an oral ingestion of the solution changed very quickly and reached the peak level at 10 to 15 minutes, and totally gastrectomized patients had greater % change after the ingestion than subtotally gastrectomized ones. In a study of the transit of the solution including 1.5 g of acetaminophen (APAP) to the small intestine, peripheral plasma concentration of APAP increased gradually till 120 minutes in normal control, on the contrary, it reached the peak level at 15 minutes in gastrectomized patients, suggesting the difference in transit time between normal controls and gastrectomized patients.