RESORPTION WITHOUT OSTEOCLASTS (OSTEOLYSIS) 543 



the skull revealed islands of large mid-trabeciilar lacunae accom- 

 panied bv decreased matrix density ( Fig. 18 ) . 



The dog which was treated with 1000 units of hormone 24 hours 

 before sacrifice showed a considerable extension of lacunar enlarge- 

 ment and confluence (Fig. 19) as well as adjacent loss of density. 

 These changes were present in both the skull and the tibia samples 

 but they were more extensive in the former. 



Alphamcliogmphij of demineralized sections revealed some sur- 

 prising facts. ( 1 ) In the normal tibia, the periosteal lining was 

 denser than the adjacent compact bone matrix. (2) In the osteons, 

 the central portion was generally denser than the periphery (Fig. 

 20). (3) The width of dense tissue varied from one osteon to an- 

 other (Fig. 20). (4) Alternating bands of high and low density 

 were observed in the osteons and in the interstitial lamellae (Fig. 

 22). (5) Irregular zones of low densitv accompanying enlarged 

 lacunae were present mostly in interstitial tissue. 



In the trabecular bone of the skull, these zones occupied a mid- 

 trabecular position as previously described in the chick (Belanger 

 and Migicovsky, 1961; Vincent et al, 1962). 



The bones of Para-Thor-Mone-treated dogs showed a coincidence 

 between the low-density mid-trabecular and interstitial areas of the 

 microradiographs (Fig. 18) and alpharadiographs (Fig. 20). It 

 seems, however, that the areas of lower densitv were more extensive 

 in the demineralized sections. 



Demineralized stained sections of the above-mentioned material 

 showed changes which were comparable to those previously re- 

 ported in the chick. Prominent in the skull and tibia specimens of 

 the dog killed 24 hours after 1000 units of Para-Thor-Mone, these 

 were: ( 1 ) an enlargement of the osteocvtes in the sites of resorption. 



Figs. 9 and 10. Two aspects of periosteal bone in alpharadiographs of 

 mineralized celloidin sections from chicks treated with Para-Thor-Mone and 

 vitamin D. The periosteal border is in the lower part of the pictnre. ( X 88. ) 



Fig. 11. Large mid-trabecular osteocvtes surrounded by basophilic matrix 

 in section from vitamin D-treated chick. Diluted Wright stain. (X 280.) 



Fig. 12. Similar location to that of Fig. 11, in section from vitamin D-Para- 

 Thor-Mone-treated bird. Hale stain. The cytoplasm and processes of the en- 

 larged osteocytes are stained. Notice exhausted cells. ( X 748. ) 



