The officers named in this article shall receive for their services a salary to be established by law, which shall not be increased or diminished during their official terms, and they shall not, after they shall not, after the expirations of the terms of those in office at the adoption of this amendment, receive to their own use any fees, costs, perquisites of office or other compensation, and all fees that may hereafter be payable by law, for any service performed by any officer provided for in this article of the Constitution, shall be paid in advance into the state treasury.