“I’ll tell you a story. There was once a badly wounded man lying on the battle-field waiting for the surgeon to dress his wound, which was covered with flies. A lightly wounded comrade saw the flies and was going to drive them away. ‘Oh, no,’ cried the wounded man, ’don’t do that! These flies are almost gorged with my blood now and aren’t hurting me nearly so much as they did at first: if you drive them away their place will be taken at once by hungrier ones, and that will be the end of me.”
