After injections of sucrose, NaCl, and urea solutions, the flow of tissue fluid from the lungs amounted to 0.182, 0.216, and 0.152 × 10-3 ml/s per mosmol/kg of concentration difference between plasma and tissues in each gram of wet tissue weight. The extracted fluid contained less than 20% of the Na+, K+ and urea concentrations of the plasma. It was concluded that this fluid was distinctly hypotonic in comparision with the fluids of the plasma and tissue compartments both before and after the injection of hypertonic solutions.
