144 



ARTICULATIONS OF THE UPPER LIMB. 



The synovial cavity of the carpal articulations is extensive and complicated. 

 Passing between the two rows of carpal bones, it sends likewise two processes 

 between the three bones of the first row, and three between the four bones 

 of the second. It is further continued downwards into the four lower carpo- 

 metacarpal and three intermetacarpal articulations of the ulnar side. In some 

 rare cases there is continuity with the synovial membrane of the wrist-joint, 

 by deficiency of one of the interosseous ligaments between the carpal bones. 



Fig. 133. 



li 



Fig- 133. TRANSVERSE SECTION OP THE SY- 

 NOVIAL CAVITIES OP THE INFERIOR RADIO- 

 ULNAR, RADIO-CARPAL, INTERCARPAL, AND 

 CARPO-METACARPAL ARTICULATIONS. | 



1, points to the triangular fibre-cartilage 

 below the ulna ; 2, placed on the ulna, points 

 to the cavity of the sacciform synovial mem- 

 brane ; 3, external lateral, and 4, internal 

 lateral ligament, and between them the synovial 

 cavity of the wrist ; 5, scaphoid bone ; 6, semi- 

 lunar ; 7, cuneiform ; 8, 8, upper portion, and 

 8', 8', lower portion of the general synovial 

 cavity of the intercarpal and carpo-metacarpal 

 articulations ; between 5 and 6, and 6 and 7, 

 the interosseous ligaments are seen separating 

 the carpal articular cavity from the wrist- 

 joint ; between the four carpal bones of the 

 lower row, and between the magnum and 

 scaphoid the interosseous ligaments are also 

 shown ; the upper division of the synovial 

 cavity communicates with the lower between 

 10 and 11, and between 11 and 12 ; x, marks 

 one of the three interosseous metacarpal liga- 

 ments ; 9', separate synovial cavity of the first 

 carpo-metacarpal articulation ; 13, first, and 14, fifth, metacarpal bone. 



NOTE. It is to be observed that in this figure, and in others of a like kind which 

 represent the joint-cavities, the white or black lines indicating the synovial membranes 

 are, for the sake of clearness, generally represented as passing over the surfaces of the 

 articular cartilages, although this is not the case in nature. These lines therefore must 

 be held to represent merely the whole continuity of the articular, or, as they are often 

 called, the synovial surfaces. 



The pisiform bone is articulated by a fibrous capsule and synovial mem- 

 brane with the cuneiform bone. Inferiorly it is united by two strong liga- 

 ments with the unciform and fifth metacarpal bones, and is sometimes also 

 connected with other metacarpal bones ; superiorly it receives the tendon 

 of the flexor carpi ulnaris muscle. The synovial membrane is usually distinct, 

 but sometimes communicates with that of the radio-carpal articulation. 



The anterior annular ligament of the wrist is a strong and thick band, 

 which extends from the prominences made by the trapezium and scaphoid 

 bone on the radial side of the carpus, directly across to the pisiform bone 

 and unciform process, and converts the transverse arch of the carpus into 

 a ring through which the flexor tendons of the digits pass into the hand. 



The posterior annular liyament, placed at the back of the wrist, is only 

 a thickened part of the aponeurosis of the forearm. It extends from the 

 lower part of the radius, at its outer border, to the inner part of the cunei- 

 form and pisiform bones, and serves to bind down the extensor tendons. 



CONNECTION OP THE METACARPAL BONES WITH THE CARPUS, AND WITH 



EACH OTHER. 



The four inner metacarpal bones are bound together at their distal extre- 

 mities by thin fibres passing between them, and constituting on their palmar 



