RESORPTION WITHOUT OSTEOCLASTS (OSTEOLYSIS) 547 



density were obserx ed in alphaiadiogiaphs of demineralized tissues 

 (Fig. 22, arrows). 



In alpharadiographs, parallel bands of high- and low-density la- 

 mellae could also be seen (Fig. 22). These have been previously 

 observed bv Rouiller et al. (1952) and Frank et al. (1955) with the 

 electron microscope, and also bv Vincent and Mandiangu (1958) by 

 x-ray microradiography The border of the trabeculae as well as the 

 periphery of the osteonic canals were sharply defined by the presence 

 of high-densitv material ( Fig. 22 ) . 



Following intravenous administration of EDTA, the older com- 

 pact bone ( tibia ) was little affected. However, more recently formed 

 compact bone (Figs. 23, 24, and 26) and also cancellous bone to a 

 greater extent (Fig. 25) rexealed an increase in the size and fre- 

 quency of lower-density areas. These were associated with the pres- 

 ence of enlarged, confluent lacunae (Figs. 23 and 25). In the im- 

 mediate vicinity of these, sites of lower density were occasionally 

 recognized ( Fig. 25 ) as distinct from the lacuna itself. Comparably 

 located islands of low density were recorded by alpharadiography 

 of the demineralized sections (Figs. 24 and 26). 



Demineralized sections of the skull, stained with toluidine blue, 

 showed a concentration of metachromatic material in and around 

 the hypertrophic osteocytes in the islands of low density, as previ- 

 ously reported in Para-Thor-Mone-treated dogs. 



Fig. 17. Trabecular bone in tibia of young dog. Notice some kirger con- 

 fluent lacunae in dense mid-trabecular region. X-ray microradiograph. (X 144.) 



Fig. 18. A skull trabecula from a dog treated with 100 units Para-Thor- 

 Mone twice a day for 3 days. Notice more numerous large lacunae and sur- 

 rounding low density of matrix in area of resorption ( R ) . X-ray microradio- 

 graph. ( X 144.) 



Fig. 19. Part of the skull of a dog killed 24 hours after a single dose of 

 1000 units Para-Thor-Mone. Many enlarged, confluent lacunae are present. 

 X-ray microradiograph. ( x 144. ) 



Fig. 20. A portion of compact bone from the tibia of a dog treated with 

 100 units Para-Thor-Mone twice a day for 3 days. Notice high density of or- 

 ganic matrix in immediate border of large and small haversian canals; also en- 

 larged lacunae and low organic density in resorption area (R). Alpharadiograph 

 of a demineralized section. ( x 88. ) 



