Formation of Compact Bone in a Kitten
Transverse section through the tibia of a fetal kitten. Labels: P, Periosteum. O, Osteogenetic layer of periosteum showing the osteoblasts newly formed bones. B, the periosteal bone deposited in successive layers beneath the periosteum and ensheathing E, the spongy endochondral bone; represented as more deeply shaded. Within the trabeculae of endochondral spongy bone are seen the medulla, with V, veins. In the lower half of the figure the endochondral spongy bone has been completely absorbed.