The long-standing model of pigment cell origins is implicitly based upon a progressive fate restriction model of neural crest development and postulates the existence of a partially restricted progenitor common to all pigment cell types (i.e., a chromatoblast) [38] .
Sodium is the fourth most abundant element on earth, comprising about 2.6% of the earth's crust; it is the most abundant of the alkali group of metals. It is now obtained commercially by the electrolysis of absolutely dry fused sodium chloride.
Sodium /ËsoÊdiÉm/ is a chemical element with symbol Na (from New Latin natrium) and atomic number 11.It is a soft, silver-white, highly reactive metal.odium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Many sodium compounds are useful, such as sodium hydroxide (lye) for soap-making and sodium chloride for use as a de-icing agent and a nutrient (edible salt). Sodium is an essential element for all animals and some plants.