Changes in the Ultra-structure of Human Fœtal Bone during Growth

Abstract

Clark and Iball have recently reported¹ their observations on changes in the ultra-structure of bone during growth. They confirmed the findings of Caglioti et al. ², that there is no evidence of crystal orientation in the long bones of new-born rats until the second to fourth day of life. Moreover, they mention that, in investigating human fœtal bones, they did not find any orientation of the hydroxyapatite crystallites until the fourth month of intrauterine life. The latter result is not in accord with my recent work, which is based on microbeam diffraction techniques³, in the investigation of the ultra-structural organization of human fœtal bone. Diffractograms of the thin periosteal bone collar from longitudinal sections of femora from ten-week old human fœtuses show in several areas a slight but definite meridional orientation of the 002 reflexion of apatite, when recorded in a Chesley microcamera with a 20-micron collimator. However, in a diffractogram taken by the usual macrobeam technique (X-ray beam 0.25 mm. wide) through the entire bone, this orientation was no longer apparent.