packed cells: a preparation of blood cells separated from the liquid plasma
cell: (biology) the basic structural and functional unit of all organisms; they may exist as independent units of life (as in monads) or may form colonies or tissues as in higher plants and animals
law of the land: a phrase used in the Magna Carta to refer to the then established law of the kingdom (as distinct from Roman or civil law); today it refers to fundamental principles of justice commensurate with due process