184 



THE ARTICULATIONS OF THE HORSE 



but some fibers end on the large metacarpal bone. A canal for the lateral extensor 

 tendon separates a short deep band which ends on the ulnar carpal bone. Other 

 deep fibers connect the latter with the fourth carpal bone, and the fourth carpal 

 with the metacarpus. 



The internal lateral ligament (Ligamentum carpi collaterale radiale) resembles 

 the preceding in general, but is stronger and wider distally. It is attached above 

 to the internal tuberosity of the distal end of the radius and ends below on the 

 proximal ends of the large and inner small metacarpal bones. Deep fasciculi are 

 detached to the radial and second carpal bones. The first carpal bone, when pres- 

 ent, is usually embedded in the posterior part of the distal end of the ligament. 

 The posterior part of the ligament is fused with the posterior annular ligament 

 (Ligamentum carpi transversum), and concurs in the formation of a canal for 



the tendon of the flexor carpi in- 



ternus. 



A number of special short ligaments 

 connect two or more adjacent bones; only 

 the most distinct of these will be described 

 here. 



The accessory carpal bone is con- 

 nected with adjacent bones by three liga- 

 ments (Fig. 444) . The proximal one is a 

 short band which extends from the acces- 

 sory carpal in front of the groove on its 

 outer face and is inserted into the distal 

 end of the radius behind the groove for 

 the lateral extensor tendon. A middle 

 band connects the accessory with the 

 ulnar carpal. The distal ligament consists 

 of two strong bands which pass from the 

 lower margin of the accessory to the fourth 

 carpal and the proximal end of the outer 

 metacarpal bone; these bands transmit 

 the action of the muscles, which are in- 

 serted into the accessory carpal bone. 

 The other bones of the proximal row are 

 connected by two anterior or dorsal liga- 

 ments, which are transverse in direction, 

 and two interosseous ligaments. An ob- 

 lique ligament passes from an eminence 

 on the posterior surface of the radial car- 

 pal bone to a small depression on the 

 radius internal to the facet for the acces- 

 sory carpal bone. 



Two ligaments connect the proximal 

 and distal rows posteriorly. The iimer 

 one joins the radial to the second and 

 third carpal, and the outer one attaches 

 the ulnar to the third and fourth carpals. 

 The bones of the distal row are connected by two strong transverse anterior or dorsal liga- 

 ments and two interosseous ligaments. 



There are four carpo-metacarpal ligaments. Two oblicjuc anterior bands connect the third 

 carpal with the large metacarpal. Two interosseous ligaments pass downward from the inter- 

 osseous ligaments of the distal row to end in depressions in the interstices between the proximal 

 ends of the metacarpal bones. 



Internal lat- 

 eral ligament 



Metacarpal 

 tuberosity 



Internal distal 

 tuberosity of 

 radius 



Accessory car- 

 pal bone ' 



Inferior liga- 



ments of acces- - - - - 

 sory carpal 



Internal 



(second) vieta- 



carpal bone 



Fig. 147.— Left Carpal Joints op Horse, Inner View 



g, Radius; 12, large (third) metacarpal bone. (After Ellen- 



berger-Baum, Anat. fiir Kiinstler.) ^ 



Movements. — Taking the joint as a whole, the chief movements are flexion 

 and extension. In the standing position the joint is extended. When the joint is 

 flexed, slight lateral movement and rotation can be produced by manipulation. 

 The anterior part of the capsule is, of course, tense during flexion, the posterior 

 part in extension. 



The movement practi(^ally all occurs at the radio-(;arpal and intercarpal joints, the articular 

 surfaces of which are widely separated in front during flexion, but remain in contact behind. The 

 distal row remains in contact with the metacarpus. The intermediate and ulnar carpals move 

 together as one piece, but the radial does not move so far as the intermediate, so that the anterior 

 and interosseous ligaments connecting these bones become tense and oblique in direction. 



