300 DISSECTION OF THE UPPER LIMB. 



nected by the deep transverse ligament which was seen in the dissection 

 of the hand (p. 280). 



IMox OF THE METACARPAL AND CAHPAL BONES. The metacarpal 

 bones of tlie fingers are articulated with the carpal bones after one plan ; 

 but the bone of the thumb has a separate joint. 



The metacarpal bone of the thumb articulates with the os trapezium ; 

 and the ends of the bones are incased in a separate capsular ligament (fig. 

 92, 2 ). The joint is furnished with a synovial membrane which is simple 

 in its arrangement. 



The tltumb-joint possesses angular movement in opposite directions, with 

 opposition and circumduction, thus : 



Flexion and extension. When the joint is flexed the metacarpal bone 

 is brought into the palm of the hand, without the ball of the thumb being 

 turned to the tips of the fingers. Extension of the joint is very free, and 

 by it the metacarpal bone is removed from the palm towards the outer 

 border of the forearm. 



Abduction and adduction. By these movements the metacarpal bone 

 is placed in contact with, or removed from the fore finger. 



Opposition. In this movement the ball of the thumb is turned towards 

 the tip of each finger by a half circumductory motion of the metacarpal 

 bone ; and in picking up a pin the joints of the thumb, and the two last 

 joints of the fingers will be bent. 



The metacarpal bones of the fingers receive longitudinal bands from the 

 carpal bones on both aspects, thus : 



The dorsal ligaments (fig. 95) are two to each, except to the bone of 

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

 from the os trapezium and os trapezoides; those of the third metacarpal 

 are attached to the os magnurn and os trapezoides; the bone of the ring 

 finger receives its bands from the os magnum and os unciforme ; and to 

 the fifth metacarpal bone there is but one ligament from the unciform. 



The palmar ligaments (fig. 92) are weaker and less constant than the 

 dorsal. There is one to each metacarpal bone, except that of the little 

 finger. These ligaments may be oblique in direction ; and a band may be 

 divided between two, as in the case of the ligament attached to the os tra- 

 pezium and the second and third metacarpals. Sometimes one or more 

 may be wanting. 



On the ulnar side of the metacarpal bone of the middle digit is a longi- 

 tudinal lateral band, which is attached above to the os magnum and unci- 

 forme, and below to the rough uinar side of the base of the above mentioned 

 bone. Sometimes this band isolates the articulation of the last two meta- 

 carpals with the unciform bone from the remaining carpo-metacarpal joint; 

 but more frequently it is divided into two parts, and does not form a com- 

 plete partition. 



This band may be seen by opening behind the articulation between the 

 unciform and the last two metacarpal bones ; and by cutting through the 

 transverse ligaments joining the third and fourth metacarpals so as to 

 allow their separation. 



Movement. Scarcely any appreciable antero-posterior movement exists 

 in the articulations of the bases of the metacarpal bones of the fore and 

 middle fingers; but in the ring and little finders the motion is greater, with 

 slight abduction and adduction. 



Dissection. The articulating surfaces of the bones in the carpo-meta- 



