STRUCTURE AND COMPOSITION OF BONE. JOINTS. 91 



pressure in early life is well seen in the distortion of the 

 feet of Chinese ladies, produced by keeping them in tight 

 shoes; and in the extraordinary forms which some races of 

 man produce in their skulls, by tying boards on the heads of 

 the children. 



Throughout the whole of life, moreover, the bones remain 

 amoug the most easily modified parts of the Body ; although 

 judging from the fact that dead bones are the most permanent 

 parts of fossil animals we might be inclined to think other- 

 wise. The living bone, however, is constantly undergoing 

 changes under the influence of the protoplasmic cells im- 

 bedded in it, and in the living Body is constantly being ab- 

 sorbed and reconstructed. The experience of physicians 

 shows that any continued pressure, such as that of a tumor, 

 will cause the absorption and disappearance of bone almost 

 quicker than that of any other tissue; and the same is 

 true of any other continued pressure. Moreover, during life 

 the bones are eminently plastic; under abnormal pressures 

 they are found to quickly, assume abnormal shapes, being 

 absorbed and disappearing at points where the pressure 

 is most powerful, and increasing at other points; tight 

 lacing may in this way produce a permanent distortion of 

 the ribs. 



When a bone is fractured a surgeon should be called in 

 as soon as possible, for once inflammation has set in and 

 the parts have become swollen it is much more difficult to 

 place the broken ends of the bone together in their proper 

 position than before this has occurred. Once the bones are 

 replaced they must be held in position by splints or bandages, 

 or the muscles attached to them will soon displace them 

 again. With rest, in young and healthy persons complete 

 union will commonly occur in three or four weeks; but in 

 old persons the process of healing is slower and is apt to be 

 imperfect. 



Articulations. The bones of the skeleton are joined 

 together in very various ways; sometimes so as to admit 

 of no movement at all between them; in other cases so as 

 to permit only a limited range or variety of movement; and 

 elsewhere so as to allow of very free movement in many 

 directions. All kinds of unions between bones are called ar- 

 ticulations. 



Of articulations permitting no movements, those which 



