The certificate paid for a visit to a Native American medicine man who was touring the UK.
He had many talents, and it was rumoured the most popular was a cure for erectile dysfunction.
After being 'persuaded' by his wife, he made the appointment.
The time came and he wondered what he was in for.
The old man handed a potion to him, and with a grip on his shoulder warned,
"This is a powerful medicine. You take only a teaspoonful, and then say '1-2-3.'
When you do, you will become more manly than you have ever been in your life, and you can perform as long as you want."
The man was encouraged. As he walked away, he turned and asked,
"How do I stop the medicine from working?"
"Your partner must say '1-2-3-4,'" he responded,
"But be warned, when they do, the medicine will not work again until the next full moon."
He was very eager to see if it worked so he went home, showered, shaved, took a spoonful of the medicine,
and then invited his wife to join him in the bedroom.
When she came in, he took off his clothes and said, "1-2-3!"
Immediately, he was the manliest of men. His wife was excited and began throwing off her clothes, but then she asked,
"What was the 1-2-3 for?"
And that, ladies and gentlemen, is why we should never end our sentences with a preposition, because we could end up with a dangling participle.
