METHODS

The artificial kidney of the Albany Hospital used in our experiments is a 1950 model built by Olson2 according to the design of Merrill and his associates (1, 2). In all in vitro studies 26 turns of 23/32" cellophane tubing were used, providing a dialytic surface area of 21,000 sq. cm. When various prepared solutions were used in place of blood for the purpose of analysing rates of exchange of solutes and water between" blood" and bath fluid, a reservoir of 10 liters of" blood" was placed in series with the artificial kidney. The volume of bath fluid at the onset of dialysis was 100 liters in all studies and was maintained at 1010 F. Essentially constant flow was main-tained by adjusting the pump to a capacity for returning fluid to the reservoir which exceeded the actual" arterial" flow into the cellophane tubing while inflow was kept at a constant pressure headand regulated by an adjustable clamp.

Chemical analysis was as follows: urea (3), creatinine (4), non-protein nitrogen (5), uric acid (6), glucose (7), sucrose (8), amino acids (9, 10), chloride (11), bicarbo-nate (12), water (13), phenol red by photoelectric col-orimetry, and sodium and potassium by flame photometry. Inorganic phosphate, inorganic sulfate, calcium, and mag-nesium methodsare noted in a previous article (14).