The board shall designate a medical board to be composed of three physicians not eligible to participate in the system. If required, other physicians may be employed to report on special cases. The medical board shall arrange for and pass upon all medical examinations required under this part and parts VII and VIII of this chapter, shall investigate all essential statements and certificates by or on behalf of a member in connection with application for disability retirement, and shall report in writing to the board its conclusions and recommendations upon all the matters referred to it.