4J)S 



N. M. IIANCOX AND B. IJOOTIIROYD 



Some of the main topographical features of a typical embryonic 

 avian osteoclast as they would appear in a low-power electron micro- 

 graph are shown in diagrammatic form in Fig. 1. Several zones along 

 the line where the cytoplasm adjoins the bone can be differentiated 



Fig. 1. Diagrammatic representation of the main features seen in osteoclasts 

 with low-power electron microscopy. Bone matrix represented as black, above; 

 osteoclast below. Seven nuclei (N) are shown. The rectangles lettered A, B, 

 and C refer to zones discussed in detail in the text; zone A is the site of the 

 traditional "brush" or "striated" border. P, pinosome; M, mitochondrion; V, 

 cytoplasmic vesicles. 



