RESORPTION WITHOUT OSTEOCLASTS (OSTEOLYSIS) 545 



accompanied by the presence of intracellular and extracellular meta- 

 chromatic material after toluidine blue or azur I staining; (2) large 

 patches of centro-trabecular or interstitial basophilic or metachro- 

 matic material corresponding to the sites of resorption revealed by 

 x-ray microradiography and alpharadiography. 



EDTA vENOCLYSis. In normal dogs, it is possible to remove a 

 considerable amount of calcium from blood by continuous intra- 

 venous infusion of EDTA, and the blood calcium is rapidly restored 

 to the normal level after the infusion has stopped (Copp, 1957). 

 Copp and Davidson (1961) have shown that perfusion of the para- 

 thyroid glands with hypocalcemic blood (8 mg % Ca) appears to 

 release increased amounts of endogenous parathormone, which re- 

 sults in a rise in systemic blood calcium presumably due to increased 

 mobilization of this element from bone. This mechanism would ac- 

 count for the prompt replacement of calcium removed bv continuous 

 intravenous infusion of EDTA. 



As previously reported, thin sections of undemineralized dog 

 bones, cancellous as well as compact, revealed regional sites of 

 higher density. These were associated with the presence of enlarged 

 and sometimes confluent lacunae (Fig. 21). Islands of lower than 

 average density, also containing enlarged lacunae (Fig. 21), were 

 observed in x-rav microradiographs. Corresponding islands of low 



Fig. 13. Part of diaphysis of the tibia from a control rat. A mid-diaphyseal 

 band of large osteocytes shows intracellular and extracellular (capsule) meta- 

 chromatic material. P, periosteum. Toluidine blue stain. (X 144.) 



Fig. 14. Same, from a rat injected with 300 units of Para-Thor-Mone over 

 3 days. The number of large osteocytes is greatly increased. Basophilic ground 

 substance is present around these. The matrix is lamellar. P, periosteum. 

 Toluidine blue. (X 144.) 



Fig. 15. Same, from a pregnant rat injected with Para-Thor-Mone as above. 

 Large numbers of hypertrophic and metachromatic osteocytes are surrounded 

 by intensely basophilic matrix. P, periosteum. Toluidine blue. ( X 144. ) 



Fig. 16. Part of the diaphysis from a 3-week-old chick fed norethandrolone 

 (Nilevar, 0.5 gm/kg) for a week. A large number of hypertrophic osteocytes 

 are present; some are surrounded by strongly neutral red-positive matrix and 

 look altogether like chondrocvtes. P, periosteum. Neutral red-fast green, (x 

 144.) 



