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 dogs duties. 

They use him to keep crowds back, said one youngster. 

No, said another, hes just for good luck. 

A third child brought the argument to a close. They use the dogs, she said firmly, to find the fire hydrant.