38 
MAMMALIAN ANATOMY 
cells in columns as the line of ossification is approached, and the 
disappearance of the hyalin matrix between the cells in the region 
of bone formation. 
Note the small, deeply staining osteoblasts disposed in a layer 
lining the cavities thus formed, and the layers of intercellular 
substance which they are forming. Those osteoblasts which 
become included between the layers or lamellae become the bone 
cells. Look for larger multinucleate cells, osteoclasts (or bone 
destroyers), among the cells of the marrow cavities, and applied 
to the surfaces of lamellae. These, by dissolving the bone material, 
form the cavities of bone. Note the extent of periosteum over the 
surface of the bone, also portions of muscles attached to this. 
