Distribution and Dynamics of Body Fluids in Sheep

The evolution of metazoa centres around the separation of potassiumrich cell fluid from the sodium-based extracellular transport medium: the blood. More than half the energy of liver cells is used in removing sodium from the cell matrix by membrane-based active transport (50). On the surfaces of the body the absorption of sodium and prevention of its loss, is an expensive process of active transport carried out by the gut and its glands, by sweat glands or renal tubules, for the maintenance of extracellular fluid concentration and volume, as part of the total flux of energy and water.