Two cowboy friends, Wally and Dallas, each bought a horse one summer. They enjoyed riding around and doing the things that cowboys do. When winter came, however, they did not want to pay to have their horses stabled for the winter. Instead, they decided to release them in a pasture and get them in the spring.
Wally noticed a problem however, and he asked Dallas, "How will we know which horse is which when we pick them up?"
Dallas answered, "Well, I've been thinking about that, and I have the answer! We'll cut the mane off of my horse and we'll cut the tail off of yours. That way, we'll know which horse belongs to you and which belongs to me."
That seemed like a great plan, and so after the trimmings, the horses were released into the pasture. When spring came around, Wally and Dallas came to get their horses, only to discover that the mane and tail had grown back during the winter.
"Dallas, since the mane and tail have grown back, how do we know which is yours and which is mine?" Wally asked.
Dallas responded, "Well, I guess you'll have to take the black one and I'll take the white one."