“…Another equally remarkable feature of osmolality is its constant level throughout body-fluid compartments. This has been convincingly demonstrated in several different ways for mammalian serum and intracellular fluid (Buckley et al, 1958;Appelboom et al, 1958;Maffly and Leaf, 1959), and cryoscopically for human serum and other body fluids in a variety of pathological conditions (Hendry, 1962). There is, therefore, every reason for believing that in both health and disease, constant osmolality, or constant water activity, prevails throughout the intracellular, extracellular and loculated spaces of the body.…”