146 H. J. HoHLiNG, H. Themann, J. Vahl 



by calcified bands, In which calcium is obviously low, supports the view that the 

 interlamellar zones are more highly calcified than the lamellae. 



Ultra-thin sections obtained from previously decalcified osteons at the final stage 

 of ossification did not show, after treatment by phosphotungstic acid, any qualitative 

 difference from those of osteons at the initial stage of ossification. In the lamellae 

 the fibrils are closely packed in bundles and are preferentially orientated according 

 to the osteon axis, although the bundles interweave frequently at small angles. Con- 

 versely, in decalcified osteons the interlamellar cementing zone is composed of thin 

 fibrils irregularly orientated in all directions. The thick banded fibrils are few or 

 completely lacking. Where present, they show a cross-, or strongly oblique orientation 

 and pass through one lamella to the next. 



Conclusions 



The investigation under the electron microscope of the dynamics of the osteon 

 calcification reveals that after a sudden initial penetration of a large percentage of 

 the matrix by elongated needle-shaped crystallites, the apatite is laid down more 

 slowly and the areas covered by needle-shaped crystallites get larger at the expense 

 of the areas in which calcium is laid down only at the level of the main cross-banding 

 of the collagen fibrils. 



A detailed paper on this subject is in press for the "J. of Ultrastructure Res.". 



References 



AscENZi, A., and C. Fabry: Technique for dissection and measurement of refractive index 



of osteons. J. biophys. biochem. Cytol. 6, 139 (1959). 

 Glimcher, M. J.: Molecular biology of mineralized tissues with particular reference to bone. 



Rev. mod. Phys. 31, 359 (1959). 



Collagen and Apatite in Hard Tissues and Pathological 

 Formations from a Crystal Chemical Point of View 



H. J. HoHLiNG, H. Themann, J. Vahl 

 Instltut fiJr Medizinische Physik, Miinster, Deutschland 



During recent years electron microscopical investigations have been carried out 

 by us on ultrathin sections of dentine, cementum and bone (Hohling, 1960, 1961, 

 1963 a, b, c, 1964; Hohling and Pfefferkorn, 1964; Vahl and Hohling, 1964/65). 

 In these four examples of apatite mineralization on collagen we found the same 

 morphological phenomena on electron microscopical examination. 



On one hand we observed light-looking, elongated formations all of the same 

 length, arranged parallel and in rows (Fig. 1, arrow 1) which were identified as 

 apatite-crystallites by means of a combination of electron "small-area" diffraction 

 with dark-field observation. On the other hand, we observed strands of thinner 

 (0 60 — 80 A), dark-looking, longer formations frequently of unequal length which 

 in general ran parallel to the rows of light-looking crystallites (Fig. 1, arrow 2). We 

 observed these formations only in the peritubular zone of the dentine and concluded 



