§ 13. Boards of visitors. A member of the board of visitors, a manager, trustee or officer of any state charitable or other institution receiving moneys from the state treasury for maintenance and support shall be entitled to actual and necessary traveling expenses when attending meetings of the board at the office of the institution or in the performance of other official duties undertaken pursuant to a resolution of the board of visitors of which he is a member, and with the approval of the head of the department under the control of which an institution is maintained.