70 NORMAL HISTOLOGY. 



in this form that the tissue will most frequently come under his 

 observation (Fig. 55). 



Minute study of the structure of the intercellular substance of 

 bone makes it appear that the organic basis is not homogeneous, 

 but is composed of minute interlacing fibres, held together by 



FIG. 55. 



Section of decalcified bone, parallel to axis of human femur, a, longitudinal section of 

 Haversian canal giving off transverse branch to the left; b, tangential section of a trans- 

 verse branch ; c, lacuna occupied by bone-corpuscle ; d, intercellular substance deprived 

 of its earthy salts and so swollen that the canaliculi are obliterated. 



a cement or " ground " substance, containing the deposit of earthy 

 salts. To these salts, which are chiefly phosphate and carbonate 

 of calcium, the bone owes its hardness, while the fibres contribute 

 toughness and elasticity to the tissue. The general arrangement 

 of the fibres in the intercellular substance is in laminae, which have 

 a general parallel direction ; but there are occasional fibres of some 

 size which pierce these laminae in a perpendicular direction and 

 appear to bind them together, very much as a nail would hold 

 a series of thin boards in place, "Sharpey's fibres." 



Bone occurs in two forms, the compact and the cancellated. 

 These do not diifer in the nature of the tissue itself, but merely 

 in the arrangement of that tissue with respect to its sources of 

 nourishment. Where the bone is massed in compact form, as in 

 the shafts of the long bones, special means for supplying it with 

 nourishment is provided by a series of channels, the Haversian 



