4 A MANUAL OF ANATOMY 



The earthy matter imparts hardness and rigidity to the bone, 

 and is composed principally of calcium salts, of which the most 

 abundant is calcium phosphate, there being about 57 per cent, 

 of this salt present. Besides this there are calcium carbonate 

 in the proportion of about 7 per cent., and calcium fluoride in 

 the proportion of about i per cent. In addition to the calcium 

 salts there are about i per cent, of magnesium phosphate, and 

 about ^ per cent, of sodium chloride. The earthy matter may 

 be separated from the animal matter by burning a bone. The 

 first effect of the heat is to char the animal matter, which is 



Fig. I. — Longitudinal Section through the Upper End of the Femur, 

 SHOWING Compact and Cancellated Osseous Tissues. 



subsequently coisumed. When so treated a bone is said to 

 be calcined, and the process is spoken of as combustion or 

 calcination. There is left a white, chalk-like, very brittle substance, 

 which, if of small size and carefully handled, retains its original 

 shape. The slightest rough handling, however, will cause it to 

 break, or crumble into a coarse powder. Calcined bone undergoes 

 no change in shape, but it loses weight to the extent of about 

 one-third. It also loses its flexibility and elasticity. The only 

 property it now possesses is hardness. As stated, it is also very 

 brittle, and, by reason of this, it cannot be bent nor twisted in 



