[Maturing of fibrils and intraosseous osteogenesis as a basis for the development of lamellae and the osteon structure].

We investigated in continuation of lightmicroscopical (phasecontrast, polarized light) and statistical studies concerning the formation of lamellae and osteons electromicroscopical the nature of fibrils in different areas of the cross section of the metacarpus from a cattle fetus of 520 mm SSL. During the maturation of fibrils in a subperiostal trabecal the diameter of fibrils increased (465 to 470 A). The period (316 or 536 A) contains primarily only a broad band and a small interband. Subsequently the interband increased (221 or 215 A), but the band decreased (324 or 271 A). In the centre of trabeculae the fibrils formate microlamellae. The fibrils split later on in the medial part of the cross section in microfibrils with irregular oreintation and appear lightmicroscopical as intermediate tissue (blasse Mittellinie). At the same time new fibrils are synthesized around the osteocytes and their canaliculi. As the result of a kind of remodeling the fibrils arrange in a parallel order forming packages which appear lightmicroscopical as fibrous felts. These fibrous felts exhibits partly an periodical arrangement with a small band (164 A) and a wide interband (287 A). In a following stage in the fibrous felts lamellae are developed, the length of which increased around the medullary cavity. Firstly after the development of lamellae the definite bone fibrils are reconstituted (diameter: 530 A; band: 348 A; interband: 212 A). Apparently the osteocytes are responsible for these procedures in a stage specific synthetic and lytic activity. The modification of the nature of fibrils results probably after the dissolving of the structural glycoproteins, which stabilize the tropocollagen molecules. A reconstitution of the structural glycoproteins after formation of the lamellae induce the reconstitution of bone specific collagenfibrils. The regulating mechanism for the codification of these structural development are unknown.