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URIST, MACDONALD, MOSS, AND SKOOG 



Fig. 5B. Photomicrograph showing a typical osteon in cortical bone in osteo- 

 porosis. The osteocvtes in the inner lamellae near \ essels appear normal, whereas 

 osteocvtes in the outer lamellae (large arrow) are retracting. The lacunae in 

 the interstitial lamellae between osteons are enlarged and transformed from a 

 thin stellate to a spherical cavity either containing a pyknotic nucleus or en- 

 tirely empty (small arrow). Hematoxylin, eosin, and azure II stain, (x ap- 

 prox. 450.) 



vealed normal stellate osteocytes in both the inner and outer lamellae 

 of the growing osteons. Nearly all the nongrowing osteons had re- 

 tracting, enlarged, or devitalized osteocytes in the outer lamellae 

 ( Fig. 5C ) and empty lacunae in the interstitial lamellae. There was 

 no way of measuring the age of the inactive osteons (those with a 

 hypercalcified inner margin), but the oxytetracycline label at three 

 intervals suggested that approximately 12 weeks was the time that 



