A fence-covering system for covering the openings in fence structures, such as an animal corral or arena. The device further has an inner member disposed within the outer concentric member. Therefore, the therapeutic agent is applicable to the prevention andor treatment of various types of ophthalmic diseases, particularly corneal disorders, dry eye, asthenopia, inflammatorily ophthalmic diseases and ophthalmnic diseases caused by active oxygen. The electrodes of the at least two medial columns are arranged into rows aligned along the transverse axis. The activated alumina formed body is usable as an adsorbent, a catalyst supporting precious metal or the like.