Visscher, Maurice

Charlie Code reached his concept of the barrier by a different route. In the 1950s Code began to study the absorption of water, sodium, and potassium in the stomach and small intestine. At that time it was well known, chiefly as the result of the work of Maurice Visscher at the University of Minnesota, that there are unidirectional fluxes across the mucosa and that net flow of water and electrolytes is the result of two opposing fluxes. Visscher had said that flux from lumen to blood is out of the gut and that flux from blood to lumen is into the gut (Fig. 7-1 A). Anyone who has studied embryology knows that the lumen of the gut is outside the body and that Visscher s designation of directions is anatomically incorrect. The confusion was compounded by those who studied fluxes across everted sacs of intestine for them, out was from fluid outside the sac, and in was into fluid inside the sac. In 1960 Code proposed unambiguous nomenclature for unidirectional and net fluxes (Fig. 7-1Code s terms were not universally adopted, but I will use them here. 

Figure 7-1. A Maurice Visscher s designation of direction of fluxes in the gut. B Code s proposed designation of the direction of fluxes. (From Code CF. The semantics of the process of absorption. Perspect Biol Med 3 560-562, 1960.)...

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