Section 87. The county commissioners shall be trustees of the institutions operated under section eighty-two except in Norfolk county where there shall be seven trustees consisting of: the three Norfolk county commissioners, the chairperson of the Norfolk county advisory board or his designee, a medical doctor residing in Norfolk county who shall be appointed by the Norfolk county advisory board to serve for a term of six years, a member of the business community residing in Norfolk county who shall be appointed by the Norfolk county advisory board to serve for a term of six years and a health care consumer residing in Norfolk county who shall be appointed by the Norfolk county advisory board to serve for a term of six years; provided, however, that one of the appointees of the Norfolk county advisory board shall reside in the town of Braintree. Such trustees shall make suitable regulations for the operation of such institutions and shall appoint superintendents and other officers and employees necessary for the proper operation of the institution. Appointment of superintendents and other physicians to the staff of said institution shall be subject to the approval of the department.