The mechanical resistance of bone to localized pressures has been studied in its relationship to the microscopial structure and physical consitution of the tissue. The microhardness tester Leitz-Duremet (Vickers method) has been used.
Blocks as well as thick sections of the compacta from the diaphysis of several Vertebrate long bones have been tested; in the sections, the minute structure and the realtive degree of mineralization of the bone tissue areas tested for microhardness were always checked.
Microhardness is from 20 to 25 % higher when the imprints of the microdurimeter are made according to a plane parallel, than when performed perpendicularly, to the long axis of the collagen fibres. Microhardness is, in general, the higher the greater is the degree of calcification of bone tissue; however, this relationship is apparent only when tissue areas with identical microscopy structure are compared.
The withdrawal of moisture by oven-drying (at 38°, 60°, 120° C) determines a progressive and consisten increase in microhardness. The amount of moisture which dired bone may absorb when rehydrated seems to be equal to that which is lost by drying. A remarkable decrease in microhardness takes place after carbonization and even more after ashing of bone samples at 300° to 500° C; microhardness increases when samples are ashed at a temperature above 500°.