330 LESLIE B. AREY 



Finally comes the vexed question as to whether the osteoclasts 

 actually are bone destroyers. Kolliker ('73) was the first and 

 most persistent exponent of their bone-destroying function. He 

 believed that their presence in the Howship's lacunae of resorp- 

 tion surfaces, on ivory pegs, and on milk teeth during resorption, 

 demonstrated his thesis beyond controversy. Among the many 

 who have subscribed to these views are Wegner ('72), Morrison 

 (73), Jackson ('04), and Maximow ('10). Mallory ('11) has 

 even suggested that the erosion of bone may be accomplished 

 mechanically by the brush border. Danchakoff ('09) refers to the 

 dissolving action on bone, but calls attention to the relative 

 infrequency of osteoclasts during the erosion of calcified cartilage 

 and the irrationality of attributing the destruction of cartilage 

 solely to them. Shaffer ('81) likewise held that they have a 

 bone-destroying action, which, however, blood-vessels chiefly 

 perform. 



Howell ('90; p. 119) took a decided stand against the probabil- 

 ity of the commonly accepted osteolytic function: 



The function of these cells is unknown. The common view that they 

 are concerned in the absorption of bone (osteoclasts) seems to me to 

 rest upon very slight evidence. If we find them in developing bone 

 lying upon the cartilage trabeculae which are being absorbed, we find 

 them also on the partitions of sponge or pith, introduced into serous 

 cavities where no absorption is taking place; and the conclusion in the 

 first case that the absorption which is going on is due to the giant cells 

 (osteoclasts) is illogical. Absorption of tissues is an occurrence common 

 enough in the body, and it is difficult to understand why the absorption 

 of bone or cartilage should require the activity of a special cell, when 

 the absorption of other tissues does not. It would seem more probable 

 that this form of cell has no specific function, and that its formation 

 is, in fact, accidental, or, in a certain sense, pathological: that the 

 presence of a solid substratum leads to an abnormally rapid growth of 

 lymphoid cells, leucocytes, osteoblasts, as the case may be, and the 

 fusion of some of these to produce multinucleated giant cells. 



The evidence in favor of a dissolving activity by the osteoclasts 

 rests upon the following relations: these elements appear at the 

 onset of resorption and disappear at its cessation; they are 

 closely applied to bone, sometimes being wrapped around eroded 

 spicules (fig. 10), and sometimes occupying the so-called How- 



