CARPO-METACARPAL ARTICULATIONS. 



103 



by the tmn.*r>r$e ligament, which was seen in the dissection of the 

 hand (p. 81). 



UNION OF THE METACARPAL AND CARPAL BONES. The meta- carpal and 

 carpal bones of the fingers are articulated with the carpal bones 

 after one plan ; but the Ixme of the thumb has a separate joint. 



The metacarpal bone of tJie thumb articulates with the trapezium ; That of the 

 and the ends of the bones are encased in a capsular ligament thumb, 

 (fig. 41, 2 ), which is lined 

 by a simple synovial mem- 

 brane. 



The thumb - joint pos- 

 sesses angular movement 

 in opposite directions, with 

 opposition and circumduc- 

 t.ion, thus : 



Flexion and extension. 

 When the joint is flexed, 

 the metacarpal lx>ne is 

 brought in front of the 

 palm ; and as the move- 

 ment proceeds, the thumb 

 is gradually turned towards 

 the fingers, passing into the 

 state of opposition. In this 



way the thumb may be FlG> 44. POSTBRIOR LIGAMENTS OP THE 

 made to touch the palmar WRIST, AND CARPAL AND METACARPAL 



BONES (BOURGKRY). 



1. Posterior radio-carpal. 



2. Carpo - metacarpal capsule of the 

 thumb. 



3. 3. Transverse bands between the ex 

 bases of the metacarpal bones. 



Motion : 



bending 



and opposi- 

 tion; 



surface of any or all of the 

 fingers, the phalanges of the 

 latter being somewhat bent 

 at the same time. Exten- 

 sion of the joint is very 

 free, and by it the meta- 

 carpal bone is removed from the palm towards the outer border of 

 the forearm. 



Abduction and adduction. By these movements the thumb is and lateral 

 placed in contact with, or removed from the forefinger. 



The metacarpal bones of the fingers receive longitudinal bands Joints of 

 from the carpal bones on both aspects, thus : 



The dorsal ligaments (fig. 44) are two to each, except to the bone have dorsal 

 of the little finger. The bands of the metacarpal bone of the fore- 

 finger come from the trapezium and trapezoid : those of the third 

 metacarpal are attached to the trapezoid and os magnum ; the bone 

 of the ring finger receives its bands from the os magnum and 

 unciform ; and to the fifth metacarpal bone there is but one 

 ligament from the unciform. 



The palmar ligaments (fig. 41), usually one to each metacarpal and palmar 

 bone, are weaker and less constant than the dorsal. These liga- ba 

 ments may be oblique in direction ; and sometimes a band is divided 

 between two, as in the case of a ligament passing from the trapezium 

 to the second and third metacarpals. One or more may be wanting 



