72 



NORMA L 1IIST0L OG Y. 



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

 observation ( Fig. 56). 



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 



From a section through the bone of a roebuck. The bone cavities (lacuna) are seen from 



the side. X 850. 



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 lamina 1 , 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 differ in the nature of the tissue itself, but merely 



