114 



THE HUMAN MACHINE 



Vcifcbral 

 column 



Radius 



Vim - 

 Carpals 



Mehcarpih 



Phalanges \ 



Clavicle 

 Sternum 



- Humerus 



FeMc girdle 



Bones and Muscles. — The body is built around a framework of 

 bone^. These bones, which are bound together by tough ligaments, 

 fall naturally into two great groups : the bones of the body proper, 

 namely, the vertebral column, ribs^ breast bone, and skull, which 



form the ax'ial skeleton; and 

 the bones of the appendages, 

 the framework of the arms and 

 legs, which, together with the 

 bones attaching them to the 

 axial skeleton, form the appen- 

 dic'ular skeleton. 



To the bones are attached 

 the muscles of the body. 

 ]\Iovement is accomphshed by 

 the contraction of muscles, 

 which are attached so as to 

 cause the bones to act as levers. 

 Muscles usualh^ act in paks : 

 one muscle extends while the 

 other flexes or bends. Bones 

 also protect the nervous sys- 

 tem and other delicate organs. 

 The bony cra'nium, inclosing 

 the brain, is an example of suck 

 protection. The internal skele- 

 ton also helps to give form and 

 rigidity to the bod3^ 



Hygiene of Muscles and 

 Bones. — Young people espe- 

 cially need to know how to 

 prevent certain defects which are largely the result of bad 

 habits of posture. Posture is a position of equilibrium of the 

 body which can be maintained for some time, such as standing or 

 sitting. Standing erect is a good habit, round shoulders are an 

 indication of a bad habit. The habit of keeping a wrong position 

 of bones and muscles, once formed, is very hard to correct. 



Round shoulders are most common among people whose occu- 

 pation causes them to stoop, A wrong position at one's desk 



Skeleton of a man 



femur 



-Tibia 

 Fibula 



.Tarsals 

 Metatarsals 

 Phalanges 



