Countercurrent Exchange in Vessels of Renal Medulla

Abstract

Summary1) The countercurrent action of the renal medullary vasculature, apparently passive, is demonstrated by its differential exclusion of materials from the papilla of the kidney in order of diffusibility. 2) The structural and functional similarity in the rete mirabilia of the kidney and fish swimbladder is stressed. The differences in functional detail in the two cases are proposed to relate to differences in the materials for which gradients are being maintained.