ARTICULATION OF THE RIBS. 255 



Articulation of the Fingers. 



The first joint of the fingers has a large synovial membrane, 

 which invests the head of the metacarpal bone and the corres- 

 ponding cavities of the bones of the first phalanx. On each 

 side is a strong lateral ligament, which arise from the side of the 

 head of the metacarpal bone, and is inserted into the side of the 

 base of the first phalanx. 



Anteriorly there is also a ligament, which, although thick 

 and strong, is very flexible. It is thickened by cartilaginous 

 matter on its palmar face, which serves as a sort of pulley to the 

 tendons, and increases their power by removing them from their 

 line of action. Posteriorly the expansion of the tendons of the 

 extensor muscle, and the tendons of the interossei, have the 

 effect of a ligament. 



The different phalanges are articulated with each other in a 

 similar manner. The lateral ligaments are very strong : the 

 tendon of the extensor covers the articulation posteriorly ; and 

 anteriorly, under the flexor tendons, there is a soft, but thick 

 ligamentous substance. The metacarpal bone of the thumb 

 differs greatly from the other metacarpal bones in its articulation 

 with the wrist, as respects its motions. The articulating surfaces 

 are calculated for lateral motion as well as flexion and exten- 

 sion ; and there are no ligaments which prevent it. Its capsular 

 ligament forms a complete sac. The first joint of the thumb 

 resembles considerably that of the fingers ; and the second joint 

 resembles the last of the phalanges. 



Articulation of the Ribs. 



The ribs are connected to the bodies of the vertebrae and the 

 intervertebral cartilages, by one articulation, and to the trans- 

 verse processes of the vertebrae by another : these articulations 

 have the ordinary apparatus for motion, with capsular ligaments, 

 which in one case r pass from the heads of the ribs to the bodies 

 of the vertebrae, and in the other from the tubercles to the trans- 

 verse processes. These form what are called the costo-vertebral, 

 and costo-transverse articulations. 



