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The Osteon Calcification as Revealed by the Electron Microscope 



A. AscENzr, E. Bonucci 

 Istituto di Anatomia Patologica dell'Universita di Pisa, Pisa, Italia 



The aim of the present study is to investigate for the first time the dynamics of 

 osteon calcification using the electron microscope. For this purpose a special technique 

 was devised to examine osteons in which the calcium content as well as the orien- 

 tation of the anisothropic components had been previously established. 



Materials and method 



Longitudinally sectioned specimens from femoral ox-shafts were fixed in neutral 

 formol and ground on a glass plate to a thickness of about 30 — 40 micra. A careful 

 examination was made in order to select osteons at the initial stage of calcification 

 (i.e. having the lowest amount of calcium as determined microradiographically) and 

 osteons which had reached their highest degree of calcification. The units were chosen 

 in such a way that under the polarizing microscope they appeared evenly bright 

 according to the marked longitudinal spiral course of the fibres in successive lamellae. 



At this stage wedge-shaped bone fragments with a portion of the chosen osteon 

 on top were dissected from the section, according to the technique described by 

 AscENZi and Fabry (1959). Once the technique was mastered, it was easy to prepare 

 from each osteon two specimens shaped as in Fig. 1. They were dehydrated in alcohol 

 and embedded in Araldite. In the resin blocks the specimens were orientated in such 



