The Skeleton. 5 



too niany canals would render the bone soft and spongy. 

 The outside of bones is covered by a tough material, a 

 skin known as the periosteum, which can be stripped 

 off ; it is very strong and sensitive and contains blood 

 vessels which serve to nourish the bone beneath. In the 

 central part of the bone (medullary canal) is found the 

 marrow, which by some scientists is held to be the birth- 

 place of the blood plates (corpuscles). 



Bone is developed from temporary cartilage or gristle. 



The uses of (functions) bones are : 1. To bear weight ; 

 2. To resist the effects of concussion ; 3. To act as levers. 

 Their fitness for the first two duties depends on the qual- 

 ity (texture), substance (size) and their arrangement. 

 The soil on which an animal is raised and the feed on 

 which it is fed influences the bone. The drier the soil 

 and the harder the food the better the quality of the bone. 

 The more open (porous) bone is, the greater the liability 

 to bony deposits, examples of which are splints. The 

 hoofs indicate the quality of the bone, e. g. , flat feet and 

 soft horn mean poor quality of bone. Among horsemen, 

 the expression, "Plat bone," is often heard, such, how- 

 ever, refers to the shape of the whole leg, the desirable 

 form being razor-like, the bone forms the heavy part of 

 the razor, while the tendons (muscles) at the back of the 

 leg form the fine edge ; if there is an excess of loose 

 tissue behind, the leg looks round, feels soft and the 

 horseman utters the dictum : ' ' The bone is round and 

 spongy ! " Large muscles mean large bones on account 

 of the greater are required for attachment sites. The 

 more bones are exposed to concussion the denser and 

 stronger they should be. It is almost impossible to obtain 



