Subject to the limits contained in the City Charter and Codified Ordinances, full power and authority is hereby vested in the Civil Service Commission to adopt, enforce, interpret and, when necessary, to amend rules for the appointment, promotion, transfer, reinstatement, suspension and removal of any employee of the City in the classified service and any other employee of the classified service over which the Civil Service Commission has jurisdiction to the end that the merit system, so far as practicable, shall govern employment in such classified service.