246 



THE SKELETON 



synovial fluid. It is secreted by a thin membrane cover- 

 ing the inside of the ligaments (the synovial membrane), 

 and acts as lubricating fluid to the heads of the bones of 

 the joint. The movement of the bones is produced b}'' 

 nmscles which are attached to them by inelastic cords 

 called tendons. We shall discuss these attachments fur- 

 ther in our study of the muscles. The roughened and 

 enlarged heads of the joining bones are special adapta- 

 tions to the need of surface for the attachment of the 

 ligaments and muscles. 



All movable joints show the above structure, namely, 

 smooth cartilage pads where the bones are in contact, syno- 

 vial fluid as a lubricant, ligaments to hold the bones in 

 place, and a syno\aal membrane to line these ligaments and 



Pelvic Bone 

 Synovial Membvana 



Id of Femur 

 ■Round Ligament 



Capsular Ligament 



Pig. 100— Section of ball and socket joint. 



produce the synovial fluid. The direction of movement of 

 a joint is determined by the form of union and the method 



