LONGITUDINAL VARIATION IN MECHANICAL COMPETENCE OF BONE ALONG THE AVIAN HUMERUS

Vickers microhardness tests were used to gauge the mechanical 'compete nce' (ability to resist bending and failure) of cortical and trabecula r bone along the humeri of three bird species, Hardness was greatest a t the midlength portion of the shaft. The mean hardness of trabeculae, where present, was between 78.7 and 90.9 % of that of the adjacent co rtical bone. The possible causes of this are briefly discussed. Microh ardness tests offer the opportunity to gauge differences in mechanical properties over small distances and might usefully be applied to test the homogeneity of mechanical properties within specimens for tensile or compressive tests.