Chronic traumatic encephalopathy, or C.T.E., is the name for a condition that is believed to result from major collisions—or from the accumulation of subconcussions that are nowhere near as noticeable, including those incurred in practice. It was first diagnosed, in 2002, in the brain of the Pittsburgh Steelers Hall of Fame center Mike Webster, who died of a heart attack after living out of his truck for a time. It was next diagnosed in one of Webster’s old teammates on the Steelers’ offensive line, Terry Long, who killed himself by drinking antifreeze.