The doctor's jar

There was an old man who was worried something was wrong with his penis. He decided to go to the doctor to get a diagnosis.

After some x-rays and checkups, the doctor got results.

"Looks like you have a testicle infection. I need further data, so I need you to masturbate into this jar so I can get a sample of your semen." the doctor says, handing the old man a mason jar with a lid closed tightly on it. "Come back the next day with what I asked for."

The next day, the old man comes back to the doctor with the jar.

"Wha? Old man, this jar has nothing in it!" the doctor said, frustrated.

The old man smiled sheepishly. "I tried everything," he says. "First, I tried by myself; I couldn't do it. Then, I asked my wife, she couldn't do it either. So, I asked my neighbor to try, but he couldn't do it either."

The doctor's eyes widened. "Hold on, you asked your neighbor?"

The old man sighed. "Yep, we just couldn't get that jar open."