The Total Electrolyte Content of Animals and Its Probable Relation to the Distribution of Body Water*

Although the knowledge of the total amounts as well as the composition of both extracellular and intracellular fluids of the body is necessary for understanding the metabolism of water and electrolyte, at present accurate information is limited to the concentrations of electrolytes in extracellular fluids. Since previous work (l-3) has shown that the concentrations of electrolytes in various extracellular fluids are fairly closely predicted from the concentrations in venous serum, the latter may be used to measure the concentrations in all extracellular fluids. It follows that the volume of extracellular water could be computed from the concentration. of a given ion if the total amount of that ion present in extracellular fluid were known. In the present paper these concepts are applied to analyses of whole animal bodies and organs, together with analyses of venous serum. The data permit the calculation of the total amounts of both extracellular and intracellular water, as well as the concentrations of electrolytes in these fluids.