A couple was watching a Discovery Channel special about an African bush tribe whose men all had penises 24 inches long. When males reach a certain age, a string is tied around their penises. And on the other end is a weight. After a while, the weight stretches the penis to 24 inches.
Later that evening as the husband was getting out of the shower, his wife looked down at him and said,
"How about we try the African string-and-weight procedure?"
The husband agreed and they tied a string and weight to his penis.
A few days later, the wife asked the husband, "How is our little tribal experiment coming along?"
"Well, it looks like we're about half way there" he replied.
"Wow, you've grown to 12 inches??"
"No...it's turned black."