The firings of the cartoonists employed by the McClatchy newspaper chain last week were a stark reminder of how an influential art form is dying, part of a general trend away from opinion content in the struggling print industry. Losing their jobs were Jack Ohman of California's Sacramento Bee, also president of the Association of American Editorial Cartoonists; Joel Pett of the Lexington Herald-Leader in Kentucky and Kevin Siers of the Charlotte Observer in North Carolina.