61 



such a way as best to bear the pressure or strains to which the 

 bone is liable. 



A Dry Bone. A bone 

 which has been macerated 

 or buried for a few weeks 

 and then exposed to the air, 

 is called a dry bone, and 

 may be preserved inde- 

 finitely. All the soft parts 

 have decayed away, the 

 periosteum, the marrow, and 

 the contents of the cancelli 

 and of the Haversian canals 

 have disappeared, and the 

 bone has become yellowish- 

 white in colour. If a slice 

 of the compact bone cut 

 transversely to the shaft be 

 ground down till it is very 

 thin it can be examined 

 microscopically. The Ha- 

 versian canals being cut 

 across appear as holes, and 

 around these are concentric 

 lines showing that the bone 

 is laid down in layers or 

 lamellae round the canals. 

 Examined more closely, the 

 concentric lines are seen to 

 be formed by a number of 

 irregular spaces connected 

 together arranged in circles 

 round each Haversian canal. 

 These spaces are called 

 lacunae, and from them 

 numerous minute wavy 

 canals pass inwards to open 



into the Haversian canal, 

 while others pass outwards 

 to open into the lacuna,- in 



FIG 27. Compact bone transverse section. 

 Magnified. 



lamella: of bone parallel or concentric with 

 the external surface ; /, lamellae concentric 

 with the surface next the marrow ; <-, 

 Hnvcrsian canals cut across with lamellae 

 arranged round them ; c, a canal jut 

 dividing into two; ,/, laincll.c between the 

 Haversiun >yvi.:ii>. 



