The Urinalysis
One day, John's tennis elbow was acting up and he decided to stop in and see a doctor. When he got to the doctor's office the nurse told him he could see the doctor in 15 minutes but, first he'd have to give a urine sample. John said that this was absurd but, the nurse insisted and John complied. 15 minutes later, John was ushered in to see the doctor.
"So that tennis elbow is really acting up, huh?" the doctor said.
"The nurse must have told you," said John, wondering how the Doctor knew.
"No. It was in your urinalysis." and the doctor continued to say that he had just purchased this new machine that could diagnose every physical condition with total accuracy based on the urine contents. John didn't believe a word of this but he did agree to provide another urine sample on check-up visit.
Two days later, John was sitting at the kitchen table with his wife and his teenage daughter. He was telling them about this ridiculous machine. When John decided to have a little fun with the doctor. John pissed in the bottle as did his wife and teenage daughter. Then while walking to his garage he had a brainstorm. John put a few drops of oil from his crankcase in the jar and finally beat off and put a few drops of semen in the jar. He drove to the doctors office, shook the bottle, then handed it to the nurse. This time his urinalysis took half an hour. Finally, John was ushered in to see the doctor.
The doctor looked at him and said, "I've got some bad news, smartass. Your daughter is pregnant, your wife's got V. D., your car is about to throw a rod, and if you don't stop beating off, that tennis elbow is never gonna heal!"