In adult bony tissues the matrix in which the bone cells are embedded appears as a clear homogeneous mass, giving no visible indication of the large amounts of calcium carbonate and phosphate which are contained in it, although these salts form two thirds of its mass. The only visible evidence of the presence of these salts is to be found in newly forming, very rapidly growing bone in the fetus, where discrete particles, or separate granules, have been recognized. Adult bony tissues show only homogeneous fused masses.
The organic basis of the matrix consists of fibers formed by the bone cells, similar to those of white fibrous tissue. In bones preformed in cartilage, the cartilage is destroyed at the advancing edge of the bony growth and replaced by these fibers, which, immediately on their formation, begin to show a deposition of calcium salts in the form of very fine, minute