All fish, reptiles, amphibians, birds, and mammals carry within their veins the elements of sodium, potassium, and calcium in almost the same proportions as the oceans. For humans, salt is as essential as water. We can perish from too little salt as we can of thirst.
Salt regulates the exchange of water between our cells and their surrounding fluids.
Humans contain about eight ounces of salt. The amount of salt is regulated in our bodies by our kidneys and by perspiration. It is a compound and has a cubic crystalline form when seen under a scanning electron microscope. Part of the salt content of earth came from the breakup of rocks by frost and erosion. The salt was locked in these rocks, and as the rain fell the dissolved salts were carried into the sea.