[Observations on the structural features of the chondrocytes in the hypertrophic zone].

It has been generally accepted that the chondrocytes in the hypertrophic zone degenerate and ultimately die during the endochondral bone formation. But a few authors, on the basis of the histological and experimental examinations, suggested that a small part of the chondrocytes do not die but are transformed into osteoblasts and osteocytes. So there is no agreement on the fate of the chondrocytes in the hypertrophic zone. To make a study on this subject, the author made observations on the structural features of the chondrocytes in the hypertrophic zone of the mandibular condyle. The mandibular condyles of the S. D. rats (3 weeks old) are used in this study. Most of the chondrocytes of the mandibular condyle progress to hypertrophy, degeneration and ultimately die. But a small part of them survive and are released from the cartilage lacunae into the bone marrow. Moreover, the chondrocytes which survive are classified into two series. In one series, the chondrocytes herdly progress to hypertrophy and become •gdark cells•h in the bone marrow. In the other series, the chondrocytes progress to hypertrophy to some extent and become •glight cells•h in the bone marrow.