ARTICULATIONS OF THE ANTERIOR LIMBS. 



201 



Fig. 129. 



Synovial membrane. — This lines all the ligaments, and is prolonged above 

 and below, between the carpal bones, to facilitate the gliding of their articular 

 facets. Two upper prolongations ascend between the three first bones of the 

 antibrachial row, to cover the inferior face of the interosseous ligaments uniting 

 them. Two other prolongations descend between the carpal bones of the second 

 row ; the external, after covering the first interosseous ligament, passes between 

 it and the corresponding anterior ligament, and communicates with the synovial 

 capsule of the carpo-metacarpal articulation. The internal 

 forms a cul-de-sac which rests on the interosseous ligament. 



Carpo-Metacarpal Articulation. — The carpal bones of 

 the second row articulate with the superior extremity of the 

 metacarpal bones, constituting a planiform diarthrosis. 



Articular surfaces. — These are, on each side, plane facets 

 more or less inclined one on the other, and continued between 

 each other. The largest is in the middle, and is generally 

 hollowed by a small, shallow, synovial fossette. 



Mode of union. — There are the four great common liga- 

 ments, and also six specicd ligaments .- two anterior, two posterior, 

 and two interosseous. 



Of the two anterior ligaments (Fig. 129, 2, 2), one is divided 

 into two distinct bands, and unites the second bone to the 

 principal metacarpal ; the other, concealed by the external 

 lateral ligament, attaches the first bone to the head of the ex- 

 ternal metacarpal bone. 



The two posterior Hgaments described by Rigot do not 

 appear to us to be suificiently distinct from the great ligament 

 to merit a special description. 



The two interosseous ligaments, completely overlooked by 

 that able anatomist, start from the interstices which separate 

 the median metacarpal bone from the lateral metacarpals, and 

 join the interosseous ligaments of the second row ; they are 

 thick and short. We have sometimes noted one or other of 

 them to be absent. 



Synovial membrane. — This communicates, as indicated above, with the 

 synovial capsule of the preceding articulation. It furnishes a superior cul-de-sac, 

 which rests on the interosseous ligament interposed between the two last cai-pal 

 bones of the second row. Two inferior culs-de-sac descend into the inter- 

 metacarpal arthrodial articulations. 



Ligaments common to the three preceding Articulations. — As before 

 mentioned, these are four in number : two lateral, one anterior, and one 

 posterior. 



a. The externcd lateral ligament (Figs. 129, 3 ; 130, 3) is a thick funicular cord 

 composed of two orders of fibres — a deep-seated and a superficial order, slightly 

 crossed. It leaves the external and inferior tuberosity of the radius, descends 

 vertically to the side of the carpus, transmits a fasciculus to the first bone of the 

 upper row, gives off another fasciculus which stops at the external bone of the 

 second row, and terminates on the head of the corresponding metacarpal bone. 

 Traversed obliquely by the lateral extensor of the phalanges, this ligament covers 

 the external carpal bones. In front, it is united to the capsular ligament ; near 

 its inferior extremity, it is confounded with the strong ligament which joins the 



carpal articula- 

 tions (front 

 view). 



1, 1, Anterior liga- 

 ments uniting the 

 carpal bones of 

 each row ; 2, 2, an- 

 terior ligaments 

 proper to the 

 carpo -metacarpal 

 articulation ; 3. 

 common external 

 ligament ; 4, com- 

 mon internal liga- 

 ment. 



