BONE STRUCTURE. 



715 



scope with a power of 200 linear, we shall see the Haversian 

 canals very plainly, and around them a series of concentric 

 bony laminae, from three to ten or twelve in number. If 

 the section should consist of the entire circle of the shaft, 

 we shall notice, besides the concentric laminae round the 

 Haversian canals, two other series of laminae, the one 

 around the outer margin of the section, the other round 

 the inner or medullary cavity. 

 Between the laminae is situ- 

 ated a concentric arrangement 

 of spider-like looking bodies, 

 which have, by different au- 

 thors, received the name of 

 osseous corpuscles, lacunae, or 

 bone -cells, according as to 

 whether they were ascertained 

 to be solid or hollow: these 

 bone- cells have little tubes or 

 canals radiating from them, 

 which are termed canaliculi. 

 The average length of the 

 lacunae, or bone-cells, in the 

 human subject is the l-2,000th Fig 5 , 8 ._ A transverse sectionlof the 



Of an inch j they are Of an Femur, or leg-bone of an Ostrich 



oval figure, and somewhat flat- ftESS ^t^VecXg 

 tened on their opposite sur- fis ure > !* wil1 ^ noticed that the 



f , L - L ,, -i j Haversian canals are much smaller 



laces, and are USUaliy abOUt and more numerous, and many of 

 One- third greater in thickness them run in a transverse direction. 



than they are in breadth; hence, as will be presently 

 shown, it becomes necessary to know in what direction 

 a specimen is cut, in order to judge of their comparative 

 size. The older anatomists supposed them, from their 

 opacity, to be little solid masses of bone ; but if the sec- 

 tion be treated with spirits of turpentine coloured with 

 alkanet-rcofc, or if it has been soaked in very liquid 

 Canada balsam for any great length of time, it can 

 then be unequivocally demonstrated that both these sub- 

 stances will gain entrance into the bone-cells through the 

 canaliculi. The bone cells, when viewed by transmitted 

 light, for the most part appear perfectly opaque ; and they 

 will appear the more opaque the nearer the section of 



