CARPO-METACARPAL. 29T 



row, lines the carpal extremities of the four inner metacarpal bones. The 

 fourth lines the adjacent surfaces of the trapezium and metacarpal bone of the 

 thumb. The fifth lines the adjacent surfaces of the cuneiform and pisiform 

 bones. 



Actions. The movement permitted in the carpo-metacarpal articulations is 

 limited to a slight gliding of the articular surfaces upon each other, the extent 



Fig. 203. Vertical Section through the Articulations at the Wrist, showing the Five Synovial 



Membranes. 



of which varies in the different joints. Thus the articulation of the metacarpal 

 bone of the thumb with the trapezium is most movable, then the fifth meta- 

 carpal, and then the fourth. The second and third are almost immovable. 

 In the articulation of the metacarpal bone of the thumb with the trapezium, 

 the movements permitted are flexion, extension, adduction, abduction, and 

 circumduction. 



3. ARTICULATIONS OF THE METACARPAL BONES WITH EACH OTHER. 



The carpal extremities of the metacarpal bones articulate with one another 

 at each side by small surfaces covered with cartilage, and connected together 

 by dorsal, palmar, and interosseous ligaments. 



The Dorsal and Palmar Ligaments pass transversely from one bone to an- 

 other on the dorsal and palmar surfaces. The Interosseous Ligaments pass be- 

 tween their contiguous surfaces, just beneath their lateral articular facets. 



The Synovial Membrane lining the lateral facets is a reflection from that 

 between the two rows of carpal bones. 



The digital extremities of the metacarpal bones are connected together by a 

 narrow fibrous band, the transverse ligament (Fig. 204) which passes trans- 

 versely across their anterior surfaces, and is blended with the ligaments of the 

 metacarpo-phalangeal articulations. Its anterior surface presents four grooves 

 for the passage of the flexor tendons. Its posterior surface blends Avith the liga- 

 ments of the metacarpo-phalangeal articulation. 



