A little girl asked her mother, "Mommy, may I take the dog for a walk around the block?"

Her mom says, "No, because the dog is in heat." 

"What does that mean?" asked the child. 

"Go ask your father. I think he is in the garage."

The little girl goes to the garage and says, "Daddy, may I take Susie for a walk around the block? I asked Mommy, but she said that Susie was in heat, and for me to ask to you."

Dad said, " Bring Susie over here" He took a rag, soaked it with gasoline, and scrubbed the dog's rear-end with it and said, "Okay,you can go now, but keep Susie on the leash and only go one time around the block."

The little girl left, and returned a short time later with the leash but without the dog. Her Dad asked, "Where is Susie?"

The little girl said, "She will be here in a minute. She ran out of gas about halfway down the block and another dog is pushing her home