Section 9. If a register, upon presentment of the grand jury, is found guilty of misconduct in his official duties, or if from bodily or mental infirmity he is incapable in person of rightly performing the same, the county commissioners, or in Suffolk county the superior court, shall, after reasonable notice, remove him from office, and may order delivery of the books, papers and other things belonging to the office to their clerk or to a new register when appointed or elected.