The equal protection clause does not detract from the right of the state justly to exert its taxing power or prevent it from adjusting its legislation to differences in situation or forbid classification in that connection, but it does require that the classification be not arbitrary, but based on a real and substantial difference having a reasonable relation to the subject of the particular legislation. Though this is the generally accepted rule as to classification, it has long been recognized by the Supreme Court that the very nature of taxation demands that the legislatures be given the widest sort of discretion in this regard. Accordingly, relatively few statutes have been declared unconstitutional on the ground of inequality.