1. The influence of various methods of preserving bone on the calcifying mechanism of the tibial epiphysial cartilage of rachitic rats was studied. An 2. Preservation by deep freezing, aqueous merthiolate, boiling, or acetone inactivated the calcifying mechanism. 3. The inactivation was reversed with calcium ions, most readily in the deep-frozen bones, less readily in the merthiolate treated bones, still less readily in the acetone stored bones, and least in boiled bones. 4. Exposure to calcium ions before preservation in the deep-freeze chest prevented inactivation. 5. The inactivation, reactivation and survival of the calcifying mechanism were confirmed by metachromasia studies. 6. The theory of the mode of action of calcium chloride on reactivation and survival of the calcifying mechanism is presented.
