Section 18. There shall be paid by the commonwealth to the secretary of the board a salary of seven hundred and fifty dollars, and to each other member thereof a salary of five hundred and seventy-five dollars, and to each member thereof his necessary traveling expenses actually incurred in attending the meetings of the board and such other expenses of the board as are incurred under section sixteen or seventeen or under sections sixty-six to seventy-three, inclusive, of chapter one hundred and twelve.