A woman takes her pet Labrador to the vet.

"My dog is cross-eyed," she says, "is there anything you can do for him?"

"Well," says the vet, "let's have a look at him".

So he picks up the dog and examines his eyes, checks his teeth, etc. Finally he says: "I'm afraid I'm going to have to put him down."

"Why? Because he's cross-eyed!?" asks the shocked woman.

"No, because he's really really heavy." replies the vet.