30 THE HUMAN HODY. 



CHEMICAL, COMPOSITION OF BONE. 



SECTION VI. 1, Bone is about two-thirds mineral, and 

 one-third animal, matter. The mineral matter is chiefly 

 phosphate of lime. This substance makes more than half 

 of the bone. The mineral and animal matter are closely 

 combined, but they can be separated in two ways: 



1. If we put a bone in a moderate fire, and burn it, it 

 will become porous and brittle, but will retain its shape. 

 The animal matter is burned out, but the mineral remains. 



2. If we put a bone in weak hydrochloric acid, and allow 

 it to remain for a few weeks, it will become as pliable as a 

 rope, and can be tied in a knot. The acid has eaten out 

 all the mineral matter, but has left the animal matter. 

 If a bone has too much mineral matter, it is brittle. 

 This is the condition of the bones of old people, and some- 

 times of younger 

 persons. They 

 break very easily. 

 In the bones of 

 children, on the 

 other hand, the 

 animal matter is 

 abundant; and 

 they will bend a 



- id. good deal before 



A BONE AFTER SOAKING IN HYDROCHLORIC ACID. flipv }vrp"")lv Til 



the disease of children called rickets, there is so little 

 mineral matter in the bones, that they are too soft. The 

 legs become bowed, the head enlarges, and the whole 

 frame gets out of shape. 



2, During childhood and youth the skeleton is assum- 



