THE SKELETON 233 



turn upon each other are called bearings, and extra precautions are taken 

 in the construction and care of the bearings to prevent friction. 



The body cannot properly be compared to any single machine, but 

 must be looked upon as a complex organization which employs a num- 

 ber of different kinds of machines in carrying on its work. The major- 

 ity of these machines are found in the skeleton. The bones are the 

 parts that are moved, and the joints serve as bearings. Connected 

 with the bones are the muscles that supply energy, and attached to 

 the muscles are the nerves that control the motion. Other parts also 

 are required for rendering the machines of the body effective in doing 

 work. These are supplied by the tissues connected with* the bones 

 and the muscles. 



HYGIENE OF THE SKELETON 



Of chief concern in the hygiene of the skeleton is the 

 proper adjustment of its parts. The efficiency of any of 

 the body machines is impaired by lack of proper adjust- 

 ment. Not only this, but because of the fact that the skele- 

 ton forms the groundwork of the whole body muscles, 

 blood vessels, nerves, everything in fact, being arranged 

 with reference to it any lack of proper adjustment of the 

 bones interferes generally with the arrangement and work 

 of tissues and organs. The displaced bones may even 

 compress blood vessels and nerves and interfere, in this 

 way, with the nourishment and control of organs remote 

 from the places where the displacements occur. For these 

 reasons the proper adjustment of the different parts of the 

 skeleton supplies one of the essential conditions for pre- 

 serving the health. 



Hygienic Importance of the Spinal Column. What has 

 been said about the adjustment of the skeleton in general 

 applies with particular force to the spinal column. The 

 spinal column serves both as the central axis of the body 

 and as the container of the spinal cord. Thirty-one pairs 



