Other vices can be concealed and cherished in secret; anger shows itself openly and appears in the countenance, and the greater it is, the more plainly it boils forth. Do you not see how in all animals certain signs appear before they proceed to mischief, and how their entire bodies put off their usual quiet appearance and stir up their ferocity? Boars foam at the mouth and sharpen their teeth by rubbing them against trees, bulls toss their horns in the air and scatter the sand with blows of their feet.