[Notes on osteoclastic resorption]

Microradiography of transverse sections in diaphyseal compact bone of old dogs shows many osteons with irregularly delimited haversian canals, very similar to a resorption cavity (fig. 1). Microradiography of longitudinal sections in the same material reveals that the enlargement of the canal affects only a fraction of its length (fig. 2). After methylene blue staining, no osteoclasts have been observed but only small mononucleated cells (fig. 3 and 4). The signification of these observations is discussed.