A demonstration of the effect of permeant and impermeant solutes, and unstirred boundary layers on osmoti flow.

Professor Donald Barron's scientific interests and achievements extend over a remarkably broad range of subjects. As a scholar and investigator he, however, did not relegate teaching to a secondary position. We hope that this modest communication will serve in a small way to remind us of the simple and lucid laboratory demonstrations that Professor Barron used so effectively and memorably in his teaching of physiology.