046 G. X. JENKINS AND C. DAWES 



concluded that the coUagen was broken down first, leadmg to the 

 release of the crystals. 



Hancox and Boothroyd, in this symposium (chapter 18), have 

 shown that detaclied collagen enters the osteoclasts, where it is 

 presumably broken down into products which might be important 

 in chelating the apatite crystals. 



Greulich ( 1961 ) showed by ultrasoft microradiography that the 

 actiye osteoclast is surrounded bv a band of organic matter 1.0 to 

 1.5 microns wide. The nature of this material is uncertain, but it 

 could contain chelating agents which might be concerned in the 

 dissolution of the crystals. 



Johnston et al. ( 1961 ) reported a large reduction in the hexosamine 

 content of bone following PTE injections in rats, implying that 

 breakdown of some constituents of the matrix was taking place. 

 The products might play a part in chelating the calcium. 



Cretin (1951), in a paper giving few details and no photomicro- 

 graphs, stated that in freehand sections of unfixed bone, indicators 

 showed that the vicinity of osteoclasts was acid up to a distance of 

 20 to 30 microns from the cell. This work would be worth repeating, 

 as it might help to decide which cells, if any, were producing acid 

 even though it would not distinguish between citric, lactic, and other 

 acids. 



The results of Dulce and Siegmund ( 1960 ) and Siegmund and 

 Dulce (1960) are also of interest. They found that inhibition of 

 carbonic anhydrase by Diamox caused a fall in the calcium of blood 

 plasma in laying hens. The explanation they suggested was that 

 inhibition of carbonic anhydrase by Diamox prevented acid secre- 

 tion and thus bone resorption by osteoclasts. This suggests that 

 carbonic acid might be important, which is support for the views of 

 Forscher and Cohn in this symposium ( chapter 22 ) . 



The Dissolution of Infected Bone 



Very little is known about the means b\' which infected bone is 

 remo\'ed. The presence of pus and inflammation will increase pres- 

 sure locally, which is probably a stimulus to osteoclast formation 

 (Hancox, 1956), and if so, the problem becomes the same as that 

 of osteoclastic removal of bone elsewhere. Dubos ( 1955) summarizes 



