METACARPO-PHALANGEAL ARTICULATION. 127 



The metacarpal bones of the four fingers are firmly connected at 

 their bases by means of dorsal and palmar ligaments, which extend 

 transversely from one bone to the other, and by interosseous liga- 

 ments which pass between their contiguous surfaces. Their lateral 

 articular facets are lined by a reflection of the great synovial mem- 

 brane of the two rows of carpal bones. 



Actions. The movements of the metacarpal on the carpal bones 

 are restricted to a slight degree of sliding motion, with the excep- 

 tion of the articulation of the metacarpal bone of the thumb with 

 the trapezium. In the latter articulation, the movements are, 

 flexion, extension, adduction, abduction, and circumduction. 



10. Metacarpo-phalangeal Articulation. The metacarpo-phalan- 

 geal articulation is a ginglymoid joint: its ligaments are four in 

 number. 



Anterior, 

 Two lateral, 

 Transverse. 



The anterior ligaments are thick and fibre-cartilaginous, and form 

 part of the articulating surface of the joints. They are grooved 

 externally for the lodgment of the flexor tendons, and by their 

 internal aspect form part of the articular surface for the head of the 

 metacarpal bone. 



The lateral ligaments are strong narrow fasciculi, holding the 

 bones together at each side. 



The transverse ligaments are strong ligamentous bands passing 

 between the anterior ligaments, and connecting together the heads 

 of the metacarpal bones of the four fingers. 



The expansion of the extensor tendon over the back of the fingers 

 takes the place of a posterior ligament. 



Actions. This articulation admits of movement in four different 

 directions, viz. of flexion, extension, adduction, and abduction, the 

 two latter being limited to a small extent. It is also capable of cir- 

 cumduction. 



11. Articulation of the Phalanges. These articulations are gingly- 

 moid joints : they are formed by three ligaments. 



Anterior, 

 Two lateral. 



The anterior ligament is firm and fibro-cartilaginous, and forms 

 part of the articular surface for the head of the phalanges. Exter- 

 nally it is grooved for the reception of the flexor tendons. 



The lateral ligaments are very strong; they are the principal 

 bond of connexion between the bones. 



The extensor tendon takes the place and performs the office of a 

 posterior ligament. 



Actions. The movements of the phalangeal joints we flexion and 

 extension, these movements being more extensive between the first 

 and second phalanges than between the second and third. 



