The Donkey and the Wolf

A Donkey, feeding in a meadow, saw a Wolf approaching to seize him, and immediately pretended to be lame. The Wolf, coming up, inquired the cause of his lameness. The Donkey said that he had a thorn in his foot, and requested the Wolf to pull it out.
The Wolf consenting, the Donkey, with his heels, kicked his teeth into his mouth and galloped away. The Wolf said: I am rightly served, for why did I attempt the art of healing, when my father only taught me the trade of a butcher?
Moral:
Everyone has his trade.