32 THE SURGICAL ANATOMY OF THE HORSE 



surface of the os magnum. The former bone shows a slight convexity 

 anteriorly and a shallow concavity posteriorly, which respond to an 

 anterior concavity and posterior convexity on the magnum. 



But the outline of the inferior surface of the magnum is almost 

 straight, and so is that of the upper surface of the large metacarpal 

 bone. Consequently the range of movement possessed by the carpo- 

 metacarpal transverse joint is restricted to that of an antero-posterior 



gliding- 



A reference to the outlines of the articular surfaces will reveal at 



a glance the preponderance in range of movement which the radio- 

 carpal joint possesses over the others. 



The articular surfaces are observed to be limited anteriorly by the 

 anterior common ligament, the attachment of which to the radius, 

 semilunar, os magnum, and large metacarpal bone are represented, and 

 it will be noticed how loose the ligament is between these points of 

 attachment. This is particularly so between its attachment to the 

 radius and semilunar bone, a point which is quite in accordance with 

 the greater degree of flexion and extension of which this joint is capable. 

 The free portions of the posterior face of the ligament are lined by the 

 synovial membranes. Running along the anterior face of the ligament 

 is the tendon of the extensor pedis muscle. Between the tendon and 

 the ligament is the small synovial bursa which facilitates the gliding of 

 the tendon. Superficially placed to the tendon is the annular band of 

 dense fascia which is placed between the tendon and the skin. 



The posterior common ligament is attached superiorly to a projection 

 of the radius, and its next point of attachment is the backwardly 

 projecting tubercle-like portion of the inferior half of the semilunar 

 bone. The length of the ligament between these attachments, when the 

 joint is in a condition of extension, is from one and a half to two inches, 

 whilst the remaining portions of the ligament — namely, those bounding 

 the intercarpal and carpo-metacarpal joints — are approximately half an 

 inch and a quarter of an inch respectively. This is another contributing 



