320 HOW DOES THE HUMAN MACHINE DO ITS WORK? 



Hygiene of muscles and bones. Young people especially need 

 to know how to prevent certain defects which are largely the result 



of bad habits of posture. 

 Good posture is a con- 

 dition of equilibrium of 

 the body which can be 

 maintained for some time, 

 such as standing or sitting 

 erect. Standing erect is 

 a good habit ; round 

 shoulders are an indica- 

 tion of a bad habit. The 

 habit of keeping a wrong 

 position of bones and mus- 

 cles, once formed, is very 

 hard to correct. 



Round shoulders are 

 most common among peo- 

 ple whose occupation 

 causes them to stoop. A 

 wrong position at one's 

 desk is among the causes. 

 Exercises which strengthen 

 (&) the muscles of the back 



Muscles work in pairs — Explain what is happening to a pg helof ul in forming the 

 the foot in (&). *. & 



habit of erect carriage. 

 Slight curvature of the spine either backward or forward is 

 helped most by exercises which tend to straighten the body, 

 such as stretching up with the hands above the head. Lateral 

 curvature of the spine, too often caused by a " hunched-up " 

 position at the school desk, may also be corrected by exer- 

 cises which tend to lengthen the spinal column. If your pos- 

 ture is not good, study your own defects and find out from an 

 orthopedic specialist just what you should do to correct it. 

 Then go to work to correct it. Remember it takes a long 

 time to overcome results of wrong posture that may have taken 

 years to form. 



