1. Young, R. W., Clin. Orth., 26, 147 (1963).
2. Ham, A. W., and Leeson, T. S., Histology, fourth ed. (J. B. Lippincott, Philadelphia, 1961). Howship, J., Roy. Med. Chir. Trans., 8, 57 (1817). Weinman, J. P., and Sicher, H., Bone and Bones, second ed. (C. V. Mosby Co., St. Louis, 1955).
3. Frost, H. M., Stain Technol., 33, 273 (1958); 34, 135 (1959). The bones examined included 58 ribs, 6 femoral head, 4 iliac crests, 7 humeri and 3 vertebrae. Dr. E. S. Zawadski and Dr. R. H. Horn made much of this material available to us.
4. Hennig, A., Zeiss Werkzeitschrift, 30, 78 (1958). Chalkley, H. W., Cornfield, J., and Park, H., Science, 110, 295 (1949). Sedlin, E., Frost, H. M., and Villanueva, A. R., Anat. Rec., 146, 201 (1963).
5. Cantarow, A., and Schepartz, B., Biochemistry, second ed.(W. B. Saunders Co., Philadelphia, 1957). Bland, J. H., Disturbances of Body Fluids, second ed. (W. B. Saunders Co., Philadelphia, 1956).