254 ARTICULATION OF THE CARPAL BONES. 



formed by the unciforme ; while another surface of the sea- 

 phoides is articulated with the trapezium and trapezoides. 

 These corresponding surfaces, formed by the two rows of carpal 

 bones, irregular as they are, compose but one articulation, 

 which is capable of a limited flexion and extension. It has a 

 synovial membrane, with two lateral ligaments, and an 

 anterior and posterior ligament ; these last, however, are short, 

 and can be best examined from within, by cutting open the 

 articulation. 



The bones of each row move laterally upon each other. 

 Their lateral surfaces, which are in contact, are covered with 

 cartilage ; and the synovial sac which exists between the first 

 and second row of bones, sends off processes between these 

 surfaces, which are disposed like the ordinary synovial mem- 

 branes in other articulations ; adhering, as is supposed, to each 

 of the cartilaginous surfaces, while they communicate with the 

 larger cavity between the two rows. 



Interosseous ligaments pass between the three outer bones 

 of the upper row, and the three inner of the lower so as to 

 intercept at these points the distribution of the synovial mem- 

 branes between the individual bones of each row. By this 

 means there is, as seen in fig. 60, including the sacciform mem- 

 brane, five synovial membranes in the wrist joint. 



Articulation of the Carpal and Metacarpal Bones. 



The metacarpal bones are connected to the last row of the 

 carpus by surfaces which are covered with cartilages, and 

 supplied with synovial membranes, as the most movable 

 articulations are ; but the ligaments which connect these bones 

 do not permit much motion between them. The ligaments 

 are all dorsal and palmar. The irregularity of the articulating 

 surfaces of the metacarpal bones of the index and middle finger 

 also contribute to restrain their motion ; and these bones accord- 

 ingly move less than the other two metacarpal bones, whose 

 surfaces are better adapted for motion. 



