A farmer is out tending to his prized bull when he notices that the bull's eyes are crossed. Since this is an expensive animal, and very important to him, he calls the vet.
The vet arrives a short while later, takes one look at the, bull and grabs a copper pipe. He tells the farmer to go stand in front of the bull, and stop him when the eyes are fixed. The vet then sticks the pipe up the bull's ass, and blows into it as hard as he can.
The bull's eyes straighten out, and so the farmer signals the vet. The vet charges fifty dollars for the visit, and leaves.
About three weeks later, the farmer notices that the bull's eyes are crossed again. He calls the vet, who returns, readies the pipe and blows again.
Once again, the bull's eyes uncross themselves.
The farmer pays the vet and returns to his business.
The another three weeks later, the bull's eyes are crossed again. Knowing the previous solution, and wanting to save a buck, the farmer calls his farm hand over to keep watch while he inserts and blows into the pipe. Nothing happens, the bull's eyes remain crossed.
Out of desperation, he suggests to the farm hand that they switch places, and that the farm hand should try blowing.
The farm hand agrees. He the pulls the pipe out of the bull's ass, turns it around, and sticks the other end in.
"What did you do that for?" The farmer asked.
"What, did you think I would blow into the same end of the pipe that your lips had touched?" The farm hand replied.
And such are the jokes that my father tells over lunch today.