Chase and the Chin Fly
“My brother and I were once ploughing corn n a Kentucky farm, I driving the horse, and he holding the plough. The horse was lazy; abut on one occasion he rushed across the field so that I, with long legs, could scarcely keep pace with him. On reaching the end of the furrow, I found an enormous chin fly fastened upon him, and knocked him off. My brother asked me what I did that for. I told him I didn’t want the old horse bitten in that way. ‘Why,’ said my brother, that’s all that made him got!” Now,’ said Mr. Lincoln, if Mr. [Salmon Chase] has a presidential chin fly biting him, I’m not going to knock him off, if it will only make his department go.”
Francis Carpenter, Six Months in the White House, p. 129-130.