METACARPO-PHALANGEAL ARTICULATIONS. 145 



facets are lined by a reflection of the great synovial membrane 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 exception of 

 the articulation of the metacarpal bone of the thumb with the trape- 

 zium. 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 fibro-cartilaginous, and form 

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

 ternally 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 be- 

 tween 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 circum- 

 duction. 



11. Articulation of tlie PJialanges. 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. Externally it is 

 grooved for the reception of the flexor tendons. 



The lateral ligaments are \ery strong; they are the principal bond 

 of connection between the bones. 



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

 posterior ligament. 



Actions. The movements of the phalangeal joints are flexion and 

 extension, these movements being more extensive between the first and 

 second phalanges than between the second and third. 



In connection with the phalanges it may be proper to examine cer- 

 tain fibrous bands termed thecce or vaginal ligammts, which serve to 

 retain the tendons of the flexor muscles in their position upon the flat 



