COMPOSITION OF BONE. 2/ 



by thoroughly burning a bone. The animal matter may 

 be obtained by soaking a bone for a few days in an acid 

 which dissolves away the minerals. 



The mineral matter by itself has still the form of the 

 bone, but is very brittle. The animal matter by itself 

 also has the form of the bone, but is soft and easily bent. 

 The two mixed together, as they are in the skeleton, 

 make our bones hard enough to support the rest of the 

 body, and tough enough not to be easily broken. The 

 animal matter also makes the bones tolerably flexible 

 and elastic: some savages make their bows from the ribs 

 of large animals. 



In childhood the animal matter, and in old age the 

 mineral matter, of bone is more abundaht than in middle 

 life. Therefore the bones of an old person are brittle 

 and easily broken, while those of a child often bend 

 when the bones of an adult would break. 



6. Gelatin. When a bone is boiled in water for several 

 hours, most of its animal matter is turned into gelatin, 

 and dissolved in the water. Gelatin is a useful food; 

 most of that which we buy for making jelly is made from 

 bones. For soup we use bones as well as meat, and by 

 long boiling extract the gelatin from them. In a piece 

 of meat as ordinarily cooked most of the gelatin remains 

 in the bones, which are therefore useful for soup and 

 should not be thrown away. 



What is the use of the minerals ? How may they be obtained sepa- 

 rate? How the animal matter? Characters of mineral matter? Of 

 the animal ? Use of having both in a bone ? At what time of life is 

 the animal matter most abundant ? Why are an old person's bones 

 easily broken ? 



6. How may we get gelatin from a bone ? Why are bones left 

 from a piece of meat useful in making soup ? 



