The Fine Structure of Bone

Abstract

X-RAY crystallographic studies by Engström and his collaborators^1,2 have shown that the apatite crystallites of bone have linear dimensions of about 220 A. × 65 A. The crystals were aligned with their long axis parallel to the collagen fibre axis, and it was suggested that there may be three such inorganic crystals for each 640 A. period of the collagen fibril. In a recent communication, Fernández-Morán and Engström³ observed a “predominance of rod- or needle-shaped apatite particles 30–40 A. wide and about 200 A. long” in thin sections of bone by means of electron microscopy. This result is in reasonable agreement with those obtained by X-ray diffraction ; but no evidence is offered that the regions of higher density present in the micrographs (which appear to have reproduced badly) were in fact due to apatite. Nor is it clear whether electron microscopy has provided any further evidence as to the manner of alignment of the particles, for Robinson and Watson⁴ have identified apatite in thin sections of bone by means of electron diffraction, and have indicated that the particles were deposited on the ‘doublet’ band region of the period of the fibril.