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 â¦ has a specific chemical identity. It (an atom) is said to be chemical element, and has all the characteristics of that element.