CHAPTER I 



BONE TISSUE AND BONE CLASSIFICATION 

 ARTICULATIONS 



Bone tissue is conspicuously a hard tissue, 

 due to the mineral or inorganic substances 

 which it contains. They are mostly phosphate 

 and carbonate of lime and form two-thirds of 

 the weight of an adult bone. The remaining 

 one-third is composed of organic or animal 

 substances, consisting of vessels, marrow, bone 

 corpuscles, and gelatinous matter. 



The mineral portion alone may be seen in 

 a bone which has been burned (thus destroy- 

 ing the organic substances). This leaves the 

 bone still hard, but very brittle and easily 

 crushed. The pale grayish color of a burned 

 bone is noticeable, the result of the loss of all 

 the marrow and blood which it contained be- 

 fore, and which gave it a pinkish tinge. 



The organic portion of a bone may be 

 shown by immersing it in dilute hydrochloric 

 acid for a few days. The mineral salts will 

 be thus dissolved out, leaving the flexible and 

 elastic organic portion which still retains the 

 shape of the bone. A long bone after the 

 lime salts are removed in this way is said to be 

 decalcified, and may be bent and twisted, or 

 even tied in a knot. 



By these experiments it is seen that the 

 mineral matter gives hardness to a bone, 

 while the animal matter gives flexibility and 

 elasticity. The proportions of the two kinds 

 of substance vary at different ages. The 

 bones of a child are soft because they have not 



This hardness is 



J 



FIG. 7. VERTICAL 

 SECTION OF A LONG 

 BONE. (Testut.) 



