A new Inmate

A new inmate at the prison was lying on his bunk at lights out. After a while, he heard someone say "Number 24", there erupted laughter from all over the prison. A little bit later, someone shouted "Number 12", and again, laughter roared thru the prison, even the guards laughed. This went on for quite some time, and the new inmate could stand it no longer, he inquired of his elderly cell-mate, "Why is everyone laughing at people quoting numbers?" The old-timer replied, "Well, young fella, we have all been in here so long, and heard each other's jokes so many times, we assigned them numbers, saves a lot of time." The new guy thought for a moment, and then shouted out "Number 19", nothing. the crickets even stopped chirping. He asked the old man, "What happened? Everyone laughed at them when the other guys told them, why didn't they laugh at mine?" The old-timer looked at him and said, "Well, young fella, some can tell em, and some can't."