The Commission may, upon its own motion, institute an inquiry into any subject matter within its jurisdiction in like manner as though a petition or complaint had been filed with it. Upon determining to institute such an inquiry the Commission shall enter an order to show cause, directing the person or corporation whose affairs are the subject matter of the investigation to appear in person or by counsel and show cause. The Commission shall thereafter proceed with the inquiry in like manner as though a petition or complaint had been filed as aforesaid.