BONES. 23 



by acids the earthy part is dissolved out, or on the other 

 hand when the "animal part is burnt out, the shape of 

 the bone is alike preserved" (Kirkes). The function of 

 the mineral matter is to give rigidity and hardness to 

 the bone; and that of the animal tissue, to bind the 

 earthy particles together, so that the bone may be able 

 to resist a considerable amount of strain and concussion. 

 This action on the part of the animal tissue of bone is well 

 shown by the fact that when a bone has been deprived 

 of its animal matter b\' intense heat, it becomes extremely 

 brittle. Also, certain constitutional changes which in- 

 juriously affect the muscular and fibrous structures of 

 the body, render the bones more or less brittle, which is 

 the case with advancing age, and when an animal has 

 been deprived of exercise for a comparatively long time. 

 Many persons think that as mankind and animals grow 

 older, the proportion of earthy matter in their bones 

 becomes greater ; but Fremy has shown by analysis that 

 age has very httle influence in this case. Rutherford 

 explains that the probable cause of bone becoming brittle 

 with age, is a molecular change in its fibrous tissue. 

 The foregoing observations show that the good quality of 

 the bones of an animal is more or less similar to that of 

 the other tissues of the body, and especially to the 

 muscles which mo\-e the bones and to which the bones 

 are attached. 



Whether a horse be intended to carry heavy burdens, 

 or to gallop over hard ground, it is always a matter 

 of the greatest importance that his bones, especially 

 those below his knees and hocks, should be strong. It 

 has been customary to state, in a vague way, that the 

 bones of Arab horses and English thorough-breds are 

 denser than those of other breeds. It would, however, 

 be more exact to say that the drier the soil on which a 

 horse has been bred and brought up, and the " harder " 

 the food upon which he has been fed, the better will be 

 the quality of his bone ; for we find that in dry, hot 



