42 ■ ANATOMY FOR NURSES [Chap. IV 



connective tissue proper, which may or may not become grad- 

 ually transformed into cartilage. Nearly all cartilages receive 

 tiieir nourishnuMit from the perichondrium which covers them, 

 and which is a moderately vascular fil)r()us membrane. 



Bone, or osseous tissue. — Bone is connective tissue in which 

 the intercellular substance which is derived from the cells is 

 rendered hard by being impregnated with mineral salts. 



The mineral, or earthy, substance which is deposited in bone, 

 and which makes it hard, consists chiefly of phosphate of calcium, 

 with about a fifth part of carbonate of calcium, and a small 

 portion of other salts. 



The organic, or soft, matter consists chiefly of blood-vessels and 

 connective tissue, and may be resolved by boiling almost entirely 

 into gelatine. 



It is possible to separate each of these substances. The min- 

 eral matter may be removed by soaking a bone in dilute acid for 

 several days. The result will be a tough, flexible, elastic substance, 

 consisting only of organic matter. The shape of the bone will be 

 preserved, but the specimen will be so free from stiffness that it 

 may be tied in a knot. 



The organic matter may be driven off by heat. As before, the 

 shape of the bone will be preserved. The specimen will consist 

 only of mineral matter, will appear white, rigid, and so brittle it 

 can bo crushed between the fingers. 



Amount of organic and inorganic matter. — The comparative 

 amount of organic and inorganic matter found in bone is dependent 

 on the age of the individual. In the foetus the tissues that later 

 become bone are either fibrous or cartilaginous. By absorption 

 of mineral substances from the blood, these tissues gradually 

 become ossified. Thus it follows that in youth the organic matter 

 is in excess. In adult life the organic matter constitutes about 

 one-third of the weight of the bone, and the inorganic matter 

 two-thirds. In old age the amount of inorganic matter is increased. 



Fractiure. — The term "fracture" is applied to the breaking of a 

 bone. As a result of the greater amount of organic matter in the 

 bones of children, they are flexible, bend easily, and do not break 

 readily. In some cases the bone bends like a bough of green wood. 

 Some of the fibres may break, but not the whole bone, hence the 

 name " green-stick fracture." It is also true that the greater 



