An 80 year old couple decide they want kids again. They visit the doctor who
suggests, since they are a little older than usual, some tests might be in
order. He hands the couple a small jar and asks them to go next door and for
the gentleman to fill it so they can test his sperm count.

A few minutes later the couple returns and hands back the jar. The doctor
exclaims, "But it's still empty!"

The main replies, "I know. I tried with my right hand, I tried with my left
hand, then I tried with both hands, and I still couldn't do it. Then my wife
tried with her right hand, then her left hand, and with both hands. She tried
with her teeth in and her teeth out, and we still couldn't get the lid off that
jar!"