Section 18. Except as otherwise provided, no money shall be paid by the commonwealth without a warrant from the governor drawn in accordance with an appropriation then in effect, and after the demand or account to be paid has been certified by the comptroller; provided, that the principal and interest on all public debts shall be paid when due without any warrant and that no appropriation shall be required for the payment of principal or income of funds held in trust by the commonwealth, or of sinking funds to meet maturing bonds, or of treasury notes issued for duly authorized temporary loans, or of corporation and other taxes collected by the commonwealth for distribution to towns, or for the investment of such funds as the state treasurer is duly authorized to invest, or for payments authorized by law out of the several prison industries funds, or for refunds of taxes or penalties or for refunds or payments of interest or costs lawfully made under chapters 58 to 65A, inclusive; and, provided, further, that the governor may, without an appropriation, draw the governor's warrant for the payment of the governor's own salary and the salaries of the justices of the supreme judicial court. No certificate shall be required from the comptroller for payment of the pay rolls of the members of the council and general court, or for the traveling and other expenses of members of the general court as provided in section 9B of chapter 3.