1. The exchange of fluid between slices of rat liver and solutions of monosaccharides, disaccharides, and sodium chloride has been studied in relation to the temperature of incubation. The point of apparent isotonicity (P.A.I.) of the tissue was defined as the concentration of the solution in which the slices neither gained nor lost weight after immersion for a period of 10 minutes.
2. In solutions of glucose, the P.A.I. of the slices was significantly lower at 4°C. than at 20°C. but similar at 20°C. and 37°C. Upon immersion for 15 to 60 minutes in 0.66 molar glucose the slices always swelled more at 37°C. than at 20°C. In solutions of sucrose change in the temperature of incubation was without effect on the hydration of the tissues.
3. In solutions of sodium chloride, the P.A.I. and the content of water, chloride, and sodium plus potassium were lower at 37°C. than at 20°C.
4. These findings emphasize the role of translocation of solute in providing an osmotic gradient for the movement of water between the tissue slices and the media.