16 



PHYSIOLOGY AND TEMPERANCE. 



2. Uses. The bones serve various purposes in the differ- 

 ent parts of the body. The skull incases and protects the 

 brain. The spinal column, with its numerous processes, pro- 

 tects the spinal cord within, while at the same time affording 

 convenient points for muscular attachment. So also the bones 

 of the chest, while formed in a great measure to protect the 

 important organs within, give attachment to muscles. It is 

 the same with regard to the lower bones 

 of the trunk, namely, the hips or pelvic 

 bones. The bones of the arm form a most 

 important member of the body. They are 

 so shaped that the muscles lying upon them 

 afford a variety and freedom of movement 

 to the arm and hand not found in any other 

 part of the body. The bones of the lower 

 extremity are mainly for the purpose of 

 sustaining the v body in the erect position, 

 and of moving it from place to place. 



3. Composition of Bone. Healthy 

 bone in a state of nature consists of an 

 organic or animal matter blended with an 

 inorganic or earthy portion, whereby elas- 

 ticity and firmness are obtained. In youth 

 Fm. 2. The Fibula, ^ ^ s about equally composed of animal and 

 or outer bone of the leg, mineral matter, in middle life it is about 



tied in a knot, after the , , 



hard mineral matter ha8 One P art animal to tw P arts mineral, and 



been dissolved out by in old age the mineral matter is largely in 

 excess. Consequently, in the young the 

 bone may be considerably bent by external force without 

 breaking, and, like a green stick, will rebound when the 

 force is removed. On the contrary, in old age any force 

 sufficiently great to bend the bone will cause a fracture; 

 while in middle life the proportion of animal and mineral 



