A nursery school teacher was delivering a station wagon full of kids home one day when a fire truck zoomed past. Sitting in the front seat of the fire truck was a Dalmatian dog. The children fell to discussing the dog's duties. "They use him to keep crowds back," said one youngster. "No," said another, he's just for good luck. A third child brought the argument to a close. "They use the dog's she said firmly, " to find the fire hydrant."