The present investigation is a further contribution to the study of mineral metabolism and is designed to throw more light on the etiology and process in osteomalacia. A correct interpretation of this process is of the greatest importance in an understanding of the metabolism of bone since the two views regarding the nature of the osteoid tissue in osteomalacia — the one, that it is an old bone from which the mineral constituents have been dissolved out, and the other that it is new bone poor in mineral constituents — are based respectively on the two opposing views regarding the metabolism of bone— the one, that bone is dead tissue not undergoing metabolism, the other, that it does have a metabolism. Anatomical investigations not having been successful in deciding between these two views, chemical methods were applied, which led to the conclusion that bony tissue, like other tissue, is continuously