ORIGIN AND FATE OF OSTEOCLASTS 331 



ship's lacunae; 7 their coloration with acid dyes often resem- 

 bles that of bone. The occasional presence of a striate border 

 (figs. 8 and 17) on the side in contact with bone might be thought 

 to indicate cellular activity (compare the brush order of the epi- 

 thelial cells of the intestine or kidney) , but this phenomenon is 

 open equally well to other interpretation. 



Against the view of the osteoclast as a causative resorptive 

 agent may be presented several objections. They are notably 

 scarce during the resorption of calcified cartilage. Howship's 

 lacunae not infrequently are seen without associated osteoclasts 

 (compare Rustizky, '74) ; this may represent a distinct method— 

 "lakunare Resorption ohne Riesenzellen" (Kaufmann, '07). A 

 'smooth resorption' of bone occurs where Howship's lacunae 

 are entirely lacking (Busch, '77), and they are often infrequent 

 where osteolysis is active. In osteomalacia, leprosy, and in 

 tumors and many inflammations (Ziegler, '78), the lime salts are 

 removed in the absence of osteoclasts — it is significant that in 

 these cases typical Howship's lacunae usually occur (Ziegler, 

 '78, et al). The absorption of various other tissues in the body 

 is accomplished without the intervention of special cells. It is 

 not impossible that the relation of osteoclast to Howship's lacu- 

 nae may be given an inverse interpretation; if the lacunae rep- 

 resent softer regions in the bone, or regions for some reason more 

 directly subjected to the resorbing principle, perhaps these 

 depressions serve merely as traps in which the giant-cells collect. 



If the osteoclasts arise largely from osteoblasts and bone cells, 

 as set forth in this communication, and if, furthermore, the sub- 

 sequent course is one of progressive degeneration, it seems un- 

 likely that such cells, which a short time before had been active 

 bone formers, now T would take over the diametrically opposed 

 function of destruction. On the contrary, the concept of progres- 

 sive degeneration seems to militate against such a view. 



7 The relation of polykaryocytes to such lacunae is demonstrated strikingly 

 during the resolution of deciduous teeth. At this time, the root may be com- 

 pletely scalloped with adjacent pits, each harboring a giant-cell. It is hoped that 

 a subsequent report will clear up the puzzling questions of the origin and signifi- 

 cance of these elements. 



