THORACIC LIMBS. 75 
The two collateral ligaments on the lateral side (Fig. 53) 
arise from the lateral epicondyle. The ventral one (4) passes 
almost directly distad and is inserted into the lateral surface of 
the proximal end of the radius about one centimeter from the 
articular surface; its inner surface is partly united to the annu- 
lar ligament (c) of the radius. The dorsal one (a) is attached 
to the lateral border of the semilunar notch of the ulna. 
Articulations of Radius and Ulna.—The proximal radio- 
ulnar articulation (Fig. 53) is by a pivot-joint or trochoid. 
The two bones are held in place by the annular ligament (Fig. 
53, ¢). This is attached on the lateral side to the dorsal border 
of the radial notch of the ulna, passes around the head of the 
radius, receiving some ligamentous fibres which come from the 
lateral epicondyle, and is attached to the coronoid process of 
the ulna. The annular ligament is closely united with the 
capsule of the joint. 
The radius and ulna are united for about their middle third 
by the thin interosseous membrane, which fills the interosseous 
space between their adjacent edges. 
The Wrist.— At the wrist or carpus there are in reality 
three joints, the first between the radius and ulna proximad 
and the first row of carpals distad, the second between the two 
rows of carpal bones, the third between the distal row of 
carpals and the metacarpals. The first two are movable joints ; 
the third is not. Each of these three joints has a capsule, and 
the bones entering into the joints are interconnected by numer- 
ous ligaments. These ligaments are named by combining the 
names of the two bones which they interconnect. Ligaments 
which interconnect bones of the same row in the carpus are 
sometimes distinguished as interosseous ligaments, as con- 
trasted with intercarpal ligaments, which connect together 
bones of different rows. According to their position the liga- 
ments may also be distinguished as dorsal, ventral, and lateral. 
Detailed descriptions and figures of all these ligaments are 
given by Strauss-Durckheim. 
Metacarpals.—The joint between the carpals and meta- 
carpals has been described. At the distal end of the meta- 
carpals the articulations with the phalanges have each a 
