It shall be unlawful for any commissioner to be concerned or personally interested, directly or indirectly, in any contract for furnishing supplies for the maintenance of the dependents of his institution district, or for the construction or improvement of property under his control. Any violation of the provisions of this act shall constitute a misdemeanor in office, and, upon conviction thereof, the party or parties so offending shall be fined in a sum not exceeding five hundred dollars, and shall be adjudged by the court to be removed from office.