CHAPTER IV. 9 



BONE. 



Bone. (T.S.) Dried long bone of man. 



Slices cut with a saw, ground thin, polished and mounted in 

 balsam. 



(L) The matrix of adult bone consists of thin layers 

 or lamellce composed of white fibrous tissue in a calcified 

 ground-substance. The fibres of alternate lamellae ai*e arranged 

 at different angles, and the lamellation is most easily recog- 

 nised where one set is cut transversely. The general 

 arrangement can be made out by observing the disposition 

 of the lacunce. These are oval flattened spaces in the 

 lamellae, the long dimensions of which correspond to the 

 planes of the latter, and which, in the absence of soft parts, 

 as in this case, are filled with air, and, in consequence, 

 appear black. (L) The outer lamellae are set parallel to 

 the surface of the shaft (periosteal lamellce). Further in 

 they form concentric Haversian systems, each of which has 

 in its centre a Haversian canal, the latter usually appears 

 opaque, through being filled with detritus. 



Among the periosteal lamellae and between the systems 

 are found here and there irregular rounded openings, the 

 Haversian spaces, which have been eroded for the deposition 

 of new systems. Where the cavity is still empty its outline 

 is pitted. In others lamellae are found lining them in greater 

 or lesser numbers, the central cavity being proportionally 

 diminished. 



