The Ox and the Dog

An ox and a dog serve for the same farmer.One day the dog arrogantly says: “How grand I am! In the daytime, I watch out for the cattle in the meadows; at night, I guard the house. But you…” “Me? How about me ?” the ox says

　　“You can only plough or draw a cart,” the dog slightly says. “Yes. It’s true,” the ox says. “But if I don’t plough, what do you guard?”