Postnatal Development of the Rat Mandible

The postnatal development of the anterior segment of the mandible was studied in the rat. A bar of cartilage was observed in the symphyseal region of a 1-day-old rat, which exhibited endochondral-like bone formation up to 21 days of age. Then the hyaline cartilage became transformed into fibrocartilage, which persisted in the midline of the adult rat mandible.