Hsia Liang-chou says that if many kinds of monkeys are caged for long periods, they will chew their own toenails completely away. If shut up too long in an enclosed space, they will become mentally abstracted, repeating a single movement over and over again.
夏良宙說，許多猴子被關久了，把自己腳指頭都啃掉了；或在封閉的籠中關久了，精神恍惚，一直重複一個動作。