Alizarin red is given intraperitoneally in dosages of 50–200 mg per kg. It then stains visibly only one generation of bone. Its deposition is studied in gross specimens and in undecalcified sections, and is controlled by comparison with serial decalcified sections. Apposition of white bone can be followed in relation to red bone on periosteal surfaces (where it presents appearances corresponding to different growth rates), on endosteal surfaces, in osteons, and in the interstitial compaction of cancellous bone. Red surfaces may be sites of deposition, stasis, or resorption. Measurements may be made from red lines, provided microscopic control is available. Removal of red bone always implies resorption. It is closely correlated with the presence of osteoclasts in control sections and with areas of surface pitting grossly. Resorbing surfaces may be precisely delimited by studying a graded series of animals. Whole surfaces or zones of stained bone are seen to “drift” toward other situations, undergoing resorptive dissolution or consolidating anew as they move relative to the newer layers. The usefulness of the dye lies in its simplicity of administration, its ready visibility, and in the fact that its persistence in bone enables the fate of areas of bone to be followed over long periods. The preparation of undecalcified sections is a problem common to many other techniques. Copyright © 1968 Wiley‐Liss, Inc., A Wiley Company
