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 is a chemical element with the chemical symbol Na. It is an alkali metal with the atomic number 11. We know that substances are made up of various atoms, and each atom has a specific chemical identity. It (an atom) is said to be chemical element, and has all the characteristics of that element.