Summary
(i) Proceeding from a consideration of the non‐diffusible constituents of the cells, the sum of the electric charges thereon, the mean intracellular pH, and an optimum or maximum membrane potential, the inorganic levels of Na, K, H, HCO2 and CI can be interpreted as physiological requirements and HCO3 and CI concentrations in turn, assuming a necessary ventilation tension of CO2. (2) Omitting considerations of the membrane potential, or treating them as of secondary importance, the optimum pH value, and in turn the K and HCO3 concentrations, are theoretically deducible by an alternative method of wider implications. (3) Including the effects of contact with the solid bone salts the concentration of the inorganic phosphate ions and minimal values for Ca and Mg ionic concentrations may also be deduced.