278 THE ARTICULATIONS OR JOINTS. 
radial end of the anterior radio-carpal ligament. By these different bands the 
palmar aspect of the joint is completely closed. 
The dorsal ligaments are more feeble than the palmar. They form a thin, loosely- 
arranged stratum, in which the only noteworthy bands are one which joins the 
scaphoid to os magnum, and another which joins cuneiform to unciform. 
The external lateral ligament (lig. collaterale carpi radiale, Fig. 217) extends 
between contiguous rough areas on the radial aspects of the scaphoid and 
trapezium. By its margins it is continuous both with the palmar and dorsal 
ligaments. 
The internal lateral ligament (lig. collaterale carpi ulnare, Fig. 217) is arranged 
like the former in regard to its margins, and by its ends it is attached to the con- 
tiguous rough ulnar surfaces of the cuneiform and unciform bones. 
Both of these lateral ligaments are directly continuous with the corresponding 
lateral ligaments of the radio-carpal joint. 
An interosseous ligament (Fig. 217) is occasionally found within the capsule, 
extending across the joint cavity between the os magnum and the scaphoid. 
The pisi-cuneiform articulation is an arthrodial diarthrosis. The mutual 
articular surfaces of the two bones are flattened and circular, and only permit of a 
small amount of giding movement. 
The joint is provided with a thin but complete capsule of fibrous tissue, which 
is specially strengthened inferiorly by two strong bands, viz. pisi-unciform (lig. piso- 
hamatum) and pisi-metacarpal (lig. pisometacarpeum, Fig. 216). Both of these 
bands extend from the lower and inner aspect of the pisiform to adjoining parts of 
the hook of the unciform and base of the fifth metacarpal bone respectively. Toa 
great extent these ligamentous bands may be regarded as extensions of the in- 
sertion of the tendon of the flexor carpi ulnaris muscle which is attached to the 
upper part of the pisiform bone. Looked at as ligaments, however, they are 
specially strong to prevent the displacement of the pisiform bone during contrac- 
tion of the muscle inserted into it. 
The synovial membranes (Fig. 217) of the carpal joints are two in number. Of 
Recessus  bhese, one is restricted to 
| _sacciformis the pisicuneiform articula- 
radioulnar tion, and is correspondingly 
a 1 simple, although occasionally 
<¢) Triangular Sk 2 
B|- fibro- the joint cavity may com- 
cartilage municate with that of the 
radio-carpal joint. 
The other synovial mem- 
brane is associated with the 
transverse carpal joint which 
extends transversely be- 
tween the two rows of carpal 
bones, with prolongations 
into the vertical intervals 
between the adjoining bones 
of each row, 2.e. the inter- 
carpal articulations. It 1s, 
therefore,an elaboratecavity, 
which may be still further 
extended, by the absence of 
interosseous ligaments, so as 
Fig. 217.—CoronaL Section through the radio-carpal, carpal, carpo- to reach the radio-carpal and 
metacarpal, and intermetacarpal joints, to show joint cavities and carpo-metacarpal series of 
interosseous ligaments (diagrammatic). eae ae 
joints. The first condition 
is rare, but the second is not uncommon, and results from the absence of the inter- 
osseous ligament between trapezium and trapezoid, or of that between trapezoid 
and os magnum. 
Trapezoid 
eae) Bas Y, 
Trapeziun 
eae 0 ae eo) 4, 
