HISTOLOGIC-STUDY OF THE FEMORAL GROWTH-PLATE IN BEAGLE DOGS

The femora of normal-growing beagle dogs were examined histologically at 6 and 12 mo of age to clarify the morphologic changes occurring in the femoral growth plate as background data for studies of chondroosse ous toxicology. Enchondral ossification was active at 6 mo of age, and the growth plate disappeared at 12 mo. The growth plate showed degrad ation of the matrix and destructive lesions at 6 mo of age. Degradatio n of the matrix was observed between the chondrocytic columns accompan ied by degeneration and disappearance of chondrocytes. Destructive cha nges were seen in the epiphyseal hyaline cartilage and proliferating a nd hypertrophic zones, resulting in disarrangement of the chondrocytic columns. Furthermore, abnormal chondrocytic proliferation of the epip hyseal hyaline cartilage zone and cleftlike fractures between the grow th plate and cortex were frequently present. No abnormalities were det ected in the articular cartilage at 6 and 12 mo of age.