Secondary cartilages in growth and development of the symphysis menti in the hamster.

The early growth and development of the symphyseal joint and pertinent adjacent regions of the mandible in the hamster, Mesocricetus auratus, are described. The joint is patent throughout life and in adults contains a large fibrocartilage which mediates mandibular movements. Evidence is presented to show that this cartilage is formed by the fusion of Meckel's cartilage with two secondary cartilages that appear within the joint space. Evidence is also presented which suggests that cells of the symphyseal cartilage have the capacity to produce bone.