There is no sadder story than Old Yeller. That’s true of both the 1956 novel, written by Fred Gipson—a Hill Country native who was born in 1908 on a farm in an unincorporated part of the area about a hundred miles northwest of San Antonio—and of the Disney film adaptation released a year after the book, which has been a cultural touchstone for many baby boomers since their childhoods.Today, only 24 percent of dog owners are baby boomers; millennials, on the other hand, make up 33 percent, the largest share among any generation—and they probably didn’t have Old Yeller on their fourth grade syllabus. This isn’t just a shame for a piece of enduring fiction—as we’ve learned in a few ways in recent years, it…