Calcification of the rabbit fetal skeleton.

The normal development of calcification in the fetal skeleton was studied in New Zealand White rabbits. The calcification process, confirmed by alizarin staining, was followed during days 16-30 of pregnancy. The process starts in the clavicle, most probably between day 15 and day 16. Simultaneously, calcification was observed in the mandible. In most of the bones of the skull, calcification starts during days 18-22. In the pectoral girdle and forelimbs the process starts in the diaphyses of the scapula, humerus, ulna and radius during days 16-19 and in the metacarpals and phalanges during days 21-26, the distal phalanges being the first to be calcified. The pelvic girdle and hindlimb follow a corresponding pattern. Calcification of the ribs commenced between days 18 and 20, and that of the vertebral column between days 19 (the atlas) and 28 (the last caudal vertebrae).