144 



A. ASCENZI, E. BONUCCI 



Transitional figures are found between the needle-shaped crystallites lying at the 

 level of the cross-bands and the bundles of elongated needle-shaped crystallites. 



Fig. 2. Ultrathin longitud 



Fig. 3. Ultrathin cross-section of an osteon at 



al stage of calcification. Explanation in text. >' 60.000 



In ultra-thin cross-sections crystallites are evenly distributed accordmg to their 

 penetration into the collagen fibrils (Fig. 3). 



