Who is Scimo from History: A Novel and what is their importance?

Scimo is an orphaned dwarf child who has learned his way around the streets of Rome. Useppe and Bella find his hiding place near the river, where he has stashed small items that he treasures. He is impressive to Useppe because he is older and because he goes to the movies, but he has actually escaped from an institution and is trying not to be found. He becomes a friend to Useppe and Bella, and they are disappointed when they find that he has gone. The reader knows that he has been found and re-institutionalized, but the little boy and his dog are unaware of what has happened to him.