Water and sodium absorption in the human intestine.

1. Studies are reported of total intestinal perfusion in man in which data relating to the absorptive capacity for water and sodium, flow rate transit time and intestinal volume have been obtained.2. A 'bolus' of radiosodium added to the steady-state perfusion has allowed measurement of bidirectional fluxes of sodium ion across the mucosa to be determined.3. The values obtained agree closely with those that can be predicted from small segmental studies reported in the literature.4. Increasing absorption capacity with increasing flow rate does not seem to reflect a true increase in absorption per unit of intestine but rather a progression to more nearly continuous flow conditions.