CLARKSON, T. W., AND S. R. TOOLE. Measurement of shortcircuit current and ion transport across the ileum. Am. J. Physiol. 206(3) : 658-668. 1964. -An apparatus is described which allowed control over both the electrical and chemical potential gradients across the isolated ileum of the rat and at the same time permitted the measurement of the transport of ions and water. Silver ions, released from the electrodes, affected ion transport. In the absence of complexing agents, the shortcircuit current (XC) fell during the 6o-min measurement period and was equal to the net sodium transport. With 10-3 M reduced glutathione in the bathing solution, the SCC was constant and equal to 94% of the sodium transport. With lo-4 M cysteine, the SCC was greatly increased. Sodium transport, also increased, was equal to 75% and chloride secretion to 20% of the EC. A mechanism by which silver ions stimulate sodium transport, is proposed. Comparison of water and salt transport between openand short-circuited tissues indicated that chloride ions were more effective in producing water movement when transported from mucosal to serosal solutions directly through the tissue (open circuit) rather than via the Ag/AgCl electrode system (short-circuit experiments).