THE LIMBS OF THE HOKSE 71 



The lateral collateral ligament (ligamentum collaterale laterale) is 

 by far the stronger — as it is also the shorter — of the two ligaments. 

 It arises from a depression on the humerus, and ends on the prominence 

 at the lateral part of the head of the radius. 



The firm union of the radius and ulna is effected by interosseous and 

 transverse ligaments. 



The interosseous ligament (ligamentum interosseum) connects the two 

 bones closely and occurs both proximal and distal to the interosseous 

 space. It corresponds to the interosseous membrane of those animals 

 in which movement (supination and pronation) between the radius 

 and ulna is relatively free. The horse has lost the power of supina- 

 tion, and the limb being in a permanent condition of pronation, the 

 fibres of the membrane (ligament) are consequently very short and 

 undergo a process of ossification as age advances. Distal to the inter- 

 osseous space, ossification is generally complete by the time adult 

 life is reached ; but proximal to the space, osseous union of the radius 

 and ulna is rare except in very advanced age. It is obvious that, 

 because of the shortness of the fibres of the interosseous ligament, 

 there is at no time appreciable movement between the horse's radius 

 and ulna : clearly ossification of the ligament abolishes all possibility 

 of movement. 



The transverse ligaments (ligamenta transversa) consist of short 

 fibres that pass from the medial and lateral surfaces of the ulna to 

 the adjacent parts of the radius. 



The pkoxlmal kadio-ulnak articulation (articulatio radioulnaris 

 proximalis) is formed by the two small, smooth areas at the back of the 

 head of the radius and corresponding facets on the opposed part of the 

 ulna, and is included within the joint capsule of the elbow. 



In the adult horse there is little or no trace of a distal radio-ulnar 

 ARTICULATION (articulatio radioulnaris distalis), because the distal end 

 (head) of the ulna, having become detached from the rest of the bone, 

 has fused with the distal end of the radius. 



The carpal articulations (articulatio carpi). — The carpal joint 

 is a complex collection of articulations between the distal end of the 

 radius, the individual carpal bones, and the bases of the three meta- 

 carpal bones. In consequence, the whole joint may be divided as 

 follows: (1) The radiocarpal articulation (articulatio radiocarpea), (2) 

 the intercarpal articulation (articulatio intercarpea) between the two 

 rows of carpal bones, (3) inte7Vsseous articulations (articulationes inter- 

 ossese) between the members of the same row of carpal bones, and (4) 

 the carpometacarpal articulation (articulatio carpometacarpea). 



Before examining the ligaments that bind the bones together, the 



