Section 76. The administrative assistant to the justices of the supreme judicial court in Suffolk county shall be appointed by the justices of said court. Said administrative assistant shall be paid by the commonwealth such sum as shall be determined by the justices of said court. The messenger to the justices of the appeals court shall be appointed by the justices of said court and shall also act as clerical assistant of said justices. His salary shall be established by the justices of said court. The messenger of the superior court in said county shall be appointed by the justices of said court and shall also act as clerical assistant of the justices of said court. His salary shall be established by the justices of said court and shall be paid by the commonwealth.