BONE STRUCTU11E. 



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 lamince round the 

 Haversian canals, two other series of laminae, the ono 

 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 

 lacunas, or bone-cells, in the 

 human subject is the l-2,000th 



J ,, Fig. 348. A transverse section lo f tJig 



ot an men ; they are of an 

 oval figure, and somewhat flat- 

 tened on their opposite sur- 

 faces, and are usually about 

 one-third greater in thickness 

 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 



Femur, or leg-bone of an Ostrich 

 (magnified 95 diameters). When 

 contrasted with the preceding 

 figure, it will be noticed that the 

 Haversian canals are much smaller 

 and more numerous, and many o 

 them run in a transverse direction. 



