sentences:  The studio discovered a trained German Shepherd named Rin Tin Tin in 1923.The canine made his debut in "Where the North Begins", a film about an abandoned pup who is raised by wolves and befriends a fur trapper.According to one biographer, Jack Warner's initial doubts about the project were quelled when he met Rin Tin Tin, "who seemed to display more intelligence than some of the Warner comics."