Here is the story according to Sporting Life magazine, May 25, 1912:
Jack Stansbury, the Louisville third-baseman, is out of the game with a broken arm. The accident happened while Jack was seated on the bench, while the Louisville Club was playng in Minneapolis. Second baseman Lynn Bell of the Colonels fouled one into the Louisville dugout. Stansbury threw up his arm to guard his head and the ball struck him on the bone, fracturing it. He will be out of the game for a month or six weeks.
If you think about it, it’s amazing that there weren’t more injuries of this fashion in those days, back when “men were men” so to speak, considering the comparatively small foul area. But it was a real rough and tumble crowd in those days, those players…I’m sure Stansbury would have winced once and said, “Hell, I ain’t goin’ to no damn doctor for this…”