POST NATAL DEVELOPMENT OF CANINE CAUDAL CERVICAL-VERTEBRAE

The morphology and post natal ossification of the fifth, sixth and sev enth cervical vertebae of 51 crossbred puppies (aged from birth to 12 weeks) were examined grossly, histologically and radiographically. At birth there were two centres of ossification, one in the vertebral bod y and one in the base of each pedicle of the neural arch. By one month of age secondary centres of ossification were present in the cranial and caudal epiphyses of the vertebral body. By two months of age these epiphyseal centres began to show signs of closure. Endochondral ossif ication of the neural arch occurred from a single centre of ossificati on within each pedicle with bony fusion of the laminae occurring by on e month of age. In addition the dimensions of the neural canal were me asured. The difference between the caudal and cranial sagittal diamete rs of each vertebra was 1 mm or less. It was concluded that, after one month of age, the shape of the neural canal can be influenced only by changes within the physes between the vertebral body and the neural a rch or by the remodelling of bone formed by intramembranous ossificati on.