"The museum park used to be surrounded by a great wrought-iron fence with spikes. They took it down when someone jumped off the roof and landed on it. They had to cut out a piece of fence, you see. The spikes had gone clear through the fellow's gut. It was one of those A.B.D.s finally giving up. A.B.D.? It means "All But Dissertation." The museum is full of them, graduate students who are incapable of finishing their dissertations. They stay on for years, living off grants, examining specimens, gathering data, wandering about the halls."