History 1509, recognized as element Essentiality demonstrated Plants: 1869 Animals: 1934 Deficiency Considered unlikely until 1955 swine parakeratosis shown to be caused by Zn deficiency conditioned human deficiency demonstrated in 1956 1961, hypogonadal dwarfism suggested to be zinc deficiency Facts 30th element in the periodic table (IIB element) MW = 65.37, co...