322 LESLIE B. AREY 



limiting membrane. Kolliker ('73) records their maximum size 

 in the human new born as 38 m x 91 n and with as many as 50 to 

 60 nuclei. I have found the measurements in the pig to run as 

 high as 65 ^ x 105 n, with a nuclear count of about 125. These 

 figures undoubtedly are too low, for the entire cell in all 

 probability extended through several sections. 



In shape, osteoclasts are rounded or have variably con- 

 spicuous processes (figs. 13 and 14). This latter configuration 

 is suggestive of amoeboid motility (compare Maximow, '10), 

 but Kolliker ('73) and Bizzozero failed to confirm this in living 

 osteoclasts examined on a warm stage. 



The cytoplasm is typically strongly oxyphilic and contains a 

 variable number of vacuoles; these Jackson ('04) believed not 

 to consist of fat, whereas Dubreuil ('10) is convinced of their 

 lipoid nature. The cytoplasm is granular, sometimes coarsely 

 so, and is notable for the usual absence of debris (compare p. 332). 

 Nuclei tend to be pyknotic, especially in the older, apparently 

 degenerating forms (fig. 16). Some nuclei appear shrunken or 

 folded (fig. 19), but convincing amitotic stages have not been 

 observed by me. 



Certain osteoclasts exhibit a brush border along the edge in 

 apposition with the bone. This border stains more intensely 

 than the rest of the cell and may be finely striate or composed 

 of coarse, block-like elements (figs. 8, 9 and 17). Some also 

 have a fringed or toothed appearance. The significance of this 

 condition is obscure. 



In regions where bone is actively forming, the osteoblasts 

 are typically separate units, columnar in shape and with baso- 

 philic cytoplasm (fig. 2, obi.) ; the nuclei tend to be placed toward 

 the end of the cell farthest from the bone matrix. As develop- 

 ment proceeds the cytoplasm diminishes in amount and in older 

 regions the still basophilic osteoblasts flatten out and lose their 

 distinct cell boundaries. There are thus formed syncytial 

 masses of variable size (fig. 1, ocl.). That such do not result 

 from overstaining with basic dyes is proved by the intense 

 oxyphilic reaction of certain other elements in the same prepara- 

 tions. Close to the basophilic syncytium in figure 1, for example, 

 was a brilliant eosinophilic osteoclast. 



